VI.] THE motrt; powers of the universe. 63 



the subversion of its equilibrium ; but other systems may 

 arise out of its ruius, or be warmed with the heat generated 

 by its destruction. It is physically quite possible that 

 meteors may continue to fall, through endless time, from 

 the regions of infinite space into the sun and the other 

 stars; that their mass and attractive power, being aug- 

 mented by the meteoric matter, may cause their planets to 

 fall on to their surfaces as gigantic meteors, still further 

 increasing their mass, and renewing their stock of heat ; 

 that the stars may in like manner rush together ; and so 

 on, absolutely without end. Some one of these three cases, 

 under some modification, must be the fact ; but it is, and 

 ever must remain, utterly useless to try to guess which is 

 the most probable. 



But though the universe may be destined for a future A past 

 without end, it camiot have existed throiigh a past with- i^™gy^ie 

 out beginning. The sun may go on accumulating meteoric 

 matter without end ; but, as his magnitude is finite, he 

 cannot have done so without beginning. Aggregation of 

 masses is always going on ; at the beginning, so far as we 

 can judge, there was no aggregation, but all matter existed 

 in a diffused state, as it appears to exist in the nebidse 

 now. Physical reasonings will bring us no farther back 

 than this : " the things which are seen were not made of 

 things which do appear." 



It will be seen that I believe in the nebular theory, Nebular 

 or, as it might be called, the condensation theory of the ^°^^' 

 origin of the stars and planets. I regard that theory as 

 no mere hypothesis. It postulates nothing as a law of 

 nature which is not independently known to be true ; and 

 its assumption, that the laws of nature have continued 

 unchanged since the beginning of things, is one that is 

 implied in all the reasonings of geology. We know that 

 the tendency of things is for masses to become more and 

 more aggregated together, and to give out heat in the pro- 

 cess : the laws of gravitation and of heat make this neces- 

 sary, and every meteor that falls on the surface of the sun 

 or of a planet is an instance of it. The nebular theory is, 

 simply, that this process has gone on from the beginning ; 



