On the Finality of Universal Change. 339 



of degradation cannot be eternal. If we could view the 

 universe as a candle not lit, then it is perhaps conceivable to 

 regard it as having been always in existence ; but if we regard 

 it rather as a candle that has been lit, we become absolutely 

 certain that it cannot have been burning from eternity, and 

 that a time will come when it will cease to burn. We are 

 led to look to a beginning in which the particles of matter 

 were in a diffuse chaotic state, but endowed with the power 

 of gravitation ; and we are led to look to an end in which 

 the whole universe will be one equally heated inert mass, and 

 from which everything like life or motion or beauty will have 

 utterly gone away." [P. 153.] 



Here the key to the whole conclusion regarding finality in 

 universal change would seem to rest in the opening sentence, 

 viz. : — u We have spoken already about a medium pervading 

 space, the office of which appears to be to degrade and ulti- 

 mately extinguish all differential motion" Does not this, 

 however, assume as a basis the old statical theory of a stag- 

 nant aether whose parts are normally at rest, and the function 

 of which of course would be to degrade all kinds of motions? 

 How about the case, however (it may be asked), under the 

 dynamical theory? — which makes the aether an active substance 

 whose particles are normally in rapid motion, and therefore 

 which would naturally tend continually to stir up and main- 

 tain motion in the parts (molecules, &c.) of the universe im- 

 mersed in the aether, and which motion developed in molecules 

 might perhaps (as a secondary consequence) conduce to a 

 translator} 7 motion of large-scale (stellar) masses, as we actu- 

 ally observe. A dynamical view of the aether cannot, at least, 

 be proved to be untenable ; and therefore the possible conse- 

 quences of such a view (as will no doubt be admitted) could not 

 be fitly excluded from any premises upon which a trustworthy 

 conclusion was intended to be based. A dynamical or kinetic 

 theory of the aether (whose particles radiate automatically in 

 streams with a very great range of path)* affords, as I have 

 pointed out, the only means of getting rid of the numerous and 

 unsatisfactory postulates attaching to Le Sage's theory of gravi- 

 tation, the ingenious idea involved in which is now accepted 

 by some eminent physicists as a hopeful explanation of the 

 phenomena of gravitation. In fact modern science goes 

 notoriously to reverse all the old statical views, and change 

 them into active dynamical theorems. 



If once a kinetic theory of the aether be entertained, then a 

 kinetic theory applied to the universe (immersed in the aether) 



* Every molecule in the universe (even in the internal parts of masses) 

 is thus aclcd on by these perturbing- streams. 



