1 88 Life and Matter [chap.x. 



the influence of gravitative attraction. The 

 asteroids have not succeeded in doing this, 

 but the planets have ; and, accordingly, one 

 of them, at any rate, has become a habitable 

 world. 



But observe that the great size and the 

 consequent retention of an atmosphere did 

 not generate the inhabitants ; it satisfied one 

 of the conditions necessary for their existence. 

 How they arose is another matter. All that 

 we have seen so far is that an aggregate of 

 bodies may possess properties and powers 

 which the separate bodies themselves possess 

 in no kind or sort of way. It is not a 

 question of degree, but of kind. 



So also, further, if the aggregate is large 

 enough, very much larger than any planet, 

 as large as a million earths aggregated 

 together, it acquires the property of 

 conspicuous radio-activity, it becomes a 

 self-heating and self-luminous body, able to 

 keep the ether violently agitated in all space 

 round it, and thus to supply the radiation 

 necessary for protecting the habitable worlds 



