674 THE POPULAR SCIENCE MONTHLY. 



sate for the radiations of luminous bodies have proved mere specu- 

 lations. We know that the sun is radiating its heat into space ; we 

 do not know that space is returning this dissipated motion, either to 

 the sun or to any other centre. We see planets and stars in various 

 stages of their progress toward the stable state ; we have no reason 

 to believe that any are in the condition of transition from the stable 

 to the unstable state. 



The moon is supposed to have already passed through most, if not 

 all, of its stages from the gaseous to the solid condition. Its atmos- 

 phere has been absorbed, its waters have retreated into its interior or 

 perhaps been converted into solids, and all its visible activities have ap- 

 parently ceased. If there still exist volcanic activities upon it, as cer- 

 tain observations seem to prove, they are probably the only ones, and 

 are themselves declining. Doubtless there are other bodies m our 

 solar system whose equilibration is even more complete than that of 

 the moon as, perhaj)s, some asteroids, or the satellites cf the outer 

 planets. They have run their long cosmical course, and have arrived 

 at last at the final state of complete, stable equilibrium. This state 

 is the goal of the whole process of evolution. It must, therefore, be 

 regarded, when viewed from this standpoint, as the state of greatest 

 perfection in the life of every aggregate. Many of the heavenly 

 bodies have certainly advanced far toward this condition, and all are 

 undoubtedly approaching it. But where is the evidence that any have 

 commenced to reverse this process ? What star is suspected of being 

 in a state of disintegration ? Where in all the universe do we see 

 solids turning into liquids, and liquids into gases ? Where and how 

 are the radiations emitted by concentrating bodies being harvested 

 again, and applied to the disintegration of completely integrated mat- 

 ter? In a word, amid all these manifest proofs of evolution, what 

 proof exists of dissolution regarded as a cosmical process ? We are 

 bound to confess that there is none. We are justified in its assump- 

 tion on a priori grounds alone, if at all. The law of the conservation 

 of energy, now so well established in all the departments of physics, 

 must be theoretically extended to the mechanics of space. This law 

 is only another expression for the indestructibility of motion. If no 

 motion can be destroyed, the same quantity must always exist in the 

 universe. And as motion is necessarily nothing more than the local 

 change of material atoms, all the solar and astral radiations must 

 continue for all time to afiect the same quantity of matter to the same 

 extent. Hence these radiations cannot be wholly lost. Still, all this 

 may be true, without afiecting the question of the dissolution of worlds. 

 The minute fraction of the sun's heat which is intercepted and ab- 

 sorbed by the different bodies of the solar system is utterly insuffi- 

 cient to ever eflfect their disintegration ; and it is continually dimin- 

 ishing as the sun itself a23proaches the term of its existence : o forti- 

 ori, no such results can ever be produced by any of the more remote 



