THE LAW OF EVOLUTION CONTINUED. 341 



taining but two. Among individual stars there are great 

 contrasts, real as well as apparent, of size; and from their 

 unlike colours, as well as from their unlike spectra, numer- 

 ous contrasts among their physical states are inferable. Be- 

 yond which heterogeneities in detail there are general hete- 

 rogeneities. Nebulae are abundant in some regions of the 

 heavens, while in others there are only stars. Here the 

 celestial spaces are almost void of objects; and there we see 

 dense aggregations, nebular and stellar together. 



The matter of our Solar System during its concentra- 

 tion has become more multiform. The aggregating gaseous 

 spheroid, dissipating its motion, acquiring more marked un- 

 likenesses of density and temperature between interior and 

 exterior, and leaving behind from time to time annular por- 

 tions of its mass, underwent differentiations that increased in 

 number and degree, until there was evolved the existing or- 

 ganized group of sun, planets, and satellites. The hetero- 

 geneity of this is variously displayed. There are the im- 

 mense contrast between the sun and the planets, in bulk and 

 in weight; as well as the subordinate contrasts of like kind 

 between one planet and another, and between the planets 

 and their satellites. There is the further contrast between 

 the sun and the planets in respect of temperature ; and there 

 is reason to suppose that the planets and satellites differ 

 from one another in their proper heats, as well as in the heats 

 which they receive from the sun. Bearing in mind that they 

 also differ in the inclinations of their orbits, the inclinations 

 of their axes, in their specific gravities and in their physical 

 constitutions, we see how decided is the complexity wrought 

 in the Solar System by those secondary re-distributions that 

 have accompanied the primary re-distribution. 



118. Passing from this hypothetical illustration, 

 which must be taken for what it is worth, without prejudice 

 to the general argument, let us descend to an order of evi- 

 dence less open to objection. 



