12 THE LESSON OF EVOLUTION 



versally admitted conclusion that comets are neither 

 more nor less than swarms of meteorites. Again, the 

 resemblance between the spectra of comets and those 

 of nebulae suggests that these also are swarms, or 

 aggregations, of meteorites. And we naturally infer 

 that the stars with similar bright-line spectra must be 

 collections of meteorites. From bright-line stars we 

 pass to those whose meteoritic origin is no longer to 

 be recognised, all having blended together. Further 

 it is claimed that by supposing variable and temporary 

 stars to be due to the meeting and entanglement of 

 two meteoritic swarms we get a better explanation of 

 the observed phenomena than any other hypothesis 

 can give. 



This meteoritic hypothesis supposes that the present 

 material Universe was at one time in a state of " cosmic 

 dust," spread irregularly through space, and moving 

 slowly in many directions. It is the original irregular 

 distribution of the cosmic dust and its irregular move- 

 ments which are the source of all the energy in the 

 Universe. We have specimens of this cosmic dust in 

 the chondroi, or spherules, of which many of the stony 

 meteorites are built up. They are small round bodies 

 of crystallised minerals, varying from microscopic 

 dimensions to the size of a marble. Of course these 

 chondroi are not the first form in which matter 

 existed. They are evidently due to chemical reactions, 

 and we could frame several different hypotheses as to 

 their origin and history. But these would be specula- 

 tions, which could not, at present, be verified ; and so 

 we must content ourselves with the chondroi as the 

 earliest form of matter known to us. 



Through the action of gravitation much of the 



