340 Mr. S. Tolver Preston on one of the Physical Premises 



appears inevitable, the stellar or cosmical bodies of the universe 

 being then regarded merely as larger-scale masses immersed 

 in a smaller-scale gas — the universe coming to be comparable 

 (in principle at least) to a gigantic gas *, of which the stellar 

 masses represent the molecules. Drawing an analogy, there- 

 fore, from the kinetic theory of gases, this view would ac- 

 cordingly point to the conclusion that, consistently with un- 

 limited variation in the energies of individual stellar masses, 

 the general distribution of energy in the universe may be at 

 present uniform, if sufficiently large samples be taken. For 

 w r e know that in the general case of portions of matter 

 moving under the kinetic theory (such as in a gas), equi- 

 librium of temperature, although perpetually tending to 

 establish itself, is only possible per unit of volume, and that 

 individual molecules may possess all sorts of temperatures. 

 It is only when sufficiently large samples of the gas (small 

 to ordinary standards of size no doubt, but each containing 



* For the further development of this idea (which may well appear 

 unfitting at the first view), I must refer to the previous papers above cited, 

 as I wish to avoid repetition here as far as possible. Naturally the first 

 thought presenting itself to the mind, in comparing the universe to a gas, 

 may be an enormous frequency of collisions occurring among the parts. 

 But this evidently need riot be, since the number of collisions may be re- 

 duced to any exteut by sufficiency of vacant space for the cosmical masses 

 to move in, which appears to be relatively almost illimitable in the case 

 of the universe. It might also appear at first sight that the translatory 

 velocity of the stellar masses (as far as we can observe this) is much too 

 great to be accounted for by any theory of equilibrium of motion between 

 them and the aether in which they are immersed, or arising, as a possible 

 secondary consequence, out of the motion developed in the constituent 

 molecules of these masses by the aether. But then it may be replied to 

 this, that, in the first place, we know nothing about either the mean 

 velocity or the mean mass of the cosmical bodies, which is the essential 

 point involved here; and, secondly, we can only perceive luminous masses 

 (which may be in the minority). Also our field of view is notoriously 

 very circumscribed. No doubt a theory (or suggestion) like the above 

 will not commend itself at an initial glance. It may even seem ex- 

 travagant at first. But then most truths appear strange at first sight, or 

 this, as a fact of notoriety, may be worth keeping in remembrance. 



The comparison of the universe to a lighted " candle " (employed in 

 the passage quoted) seems in point of principle scarcely legitimate or 

 exact, in so far as a lighted candle necessarily implies waste from chemical 

 action, which of course essentially gives an idea of finality. A com- 

 parison to a hot body would not imply waste or change of this kind ; and 

 if we conceive to ourselves a hot body placed under such conditions that 

 it cannot cool, we should then have no change. My contention is that 

 the universe is to be regarded as such a hot body which (as a whole) 

 cannot cool, but whose parts have differential temperatures, owing to 

 differential motion under the kinetic theory. It is, in one sense at least, 

 much as if we were inside a nebula of a "n^bulosite, tellement diffuse 

 que Ton en pourrait a peine soupconner l'existence," to quote an expression 

 of Laplace. 



