upon ivhich the Finality of Universal Change is based. 341 



many millions of molecules) are taken for comparison, that 

 the temperatures of the samples can be said to be equal, or 

 that equilibrium of temperature can be said to exist. My 

 contention (or suggestion) therefore is — magnify the scale, 

 and apply in broad principle the same general considerations 

 to the universe. In other words, apply the great dynamical 

 theorem developed by Joule, Clausius, and Maxwell on a grand 

 scale. It is at least so far true, that dynamical considerations 

 or mechanical principles are generally regarded as independent 

 of scale, or that this could not be a point affecting their validity, 

 whatever other reasonable grounds of objection or difficulties 

 might arise. For of course in a suggestion having any points 

 of novelty about it, it is scarcely to be expected that all will 

 appear smooth and straightforward at the outset. A little 

 unbiased thought may even be necessary to make it appear 

 worthy of examination. It is at least always conceivable 

 beforehand, that in so wide a subject some physical point 

 affecting the resulting conclusion of finality in the universe 

 may have escaped notice. And the definite manner (almost 

 approaching to an air of certainty) with which this ultimate 

 destiny of the universe is sometimes enunciated, would seem 

 to warrant great care in weighing every possible eventuality 

 in the premises upon which this view is grounded. Sir W. 

 Grove remarks on this point : — " The notion that the universe 

 is gradually equalizing its heat and tending to a chaos of 

 uniform temperature and equilibrium of force, although it may 

 be supported by the phenomena we see immediately around 

 us, seems to me like those views of the instability of the solar 

 system which Laplace negatived, and would require far more 

 cogent proof than any at present given" ( ; Correlation of 

 Physical Forces,' 6th Edition, page 69). 



It may, however, be remarked that if the idea suggested 

 here (and in former essays) should ultimately turn out to 

 have a germ of truth, it would serve to some extent the purpose 

 of reconciling rival views. For while recurring change would 

 still be possible (or, in Sir W. Grove's words, " phenomena 

 seeming to tend in one direction will turn out to be recurrent, 

 though never absolutely identical in their recurrence/' page 

 69), nevertheless equilibrium of temperature would actually 

 exist in a certain sense, (i. e. per unit of volume) * in the uni- 

 verse ; but this would not be inconsistent with the continuance 

 of conditions necessary for life. 



London, Oct. 1880. 



* If the universe be regarded as practically unlimited in extent, then 

 the size of such a unit of volume, though great compared with a planetary 

 system, would become (relatively speaking) indefinitely small. Hence 

 the theorem that equilibrium (or uniformity) of temperature tends to be 



