AND THEORY OF THE HEAVENS. 87 



of its density may have pressed so near to the centre 

 with the requisite degree of velocity; on the other hand, 

 the body in the centre itself has been heaped together 

 without distinction of those materials of all existing 

 kinds which have not attained to regular movements of 

 their own. And as the lighter materials constitute the 

 greatest portion of these various kinds of matter, it is 

 easy to see that because the heavenly body, or any of 

 the bodies revolving nearest the centre, contains as it 

 were a selection of the denser kinds of matter, while the 

 central body comprises in itself a mixture of them all 

 without distinction, the substance of the former will be 

 denser than that of the latter. And, in fact, the moon is 

 twice denser than the earth, and the earth is four times 

 denser than the sun, which according to all conjecture 

 will be surpassed by still higher degrees of density by 

 the nearer planets Venus and Mercury. 



Our attention must now be directed to the relation 

 which, according to our theory, the masses of the 

 heavenly bodies ought to have in comparison with their 

 distances, in order to test the result of our system by 

 the infallible calculations of Newton. It does not need 

 many words to make it intelligible that the central 

 body must always be the chief member of its system, 

 and consequently that the sun must be considerably 

 greater in mass than the whole of the planets : a rela- 

 tion which will also hold good of Jupiter and Saturn 

 when compared with their satellites. The central body 

 is formed by the deposit of all the particles drawn from 

 the whole range of its sphere of attraction which have 

 not been able to obtain the precise determination of 

 circular movement and the near relation to the common 



