154 Mr. S. T. Preston on the Continuance of 



the fragments or scattered parts rebound or glance off exceeds 

 the greatest velocity of approach that gravity could generate 

 in them when falling together from an indefinite distance, then 

 the degree of aggregation after the collision would be less than 

 it was before. Indeed, fixing the imagination upon a single 

 cubical element of space containing detached solid masses of 

 matter, and enclosed by a rigid envelope [other similar cubical 

 elements existing outside — and the masses being figured for the 

 instant at rest], it is then quite conceivable that such a velo- 

 city might be suddenly given to these detached masses of 

 matter that the heat developed at their mutual collisions is 

 sufficient to resolve the whole into discrete molecules (or a gas) 

 pervading the cubical envelope uniformly, i. e. so that gravity 

 is incompetent to produce any degree of aggregation (in the 

 form of clusters or nuclei) at all*. Is not a less velocity than 

 this conceivable which, when communicated to the masses, 

 would still leave them some degree of aggregation, dependent 

 on the mean velocity of translatory motion? which velocity 

 (though constant from one unit of volume to another) would 

 vary greatly from one mass to another in accordance with the 

 principles of the kinetic theory — producing corresponding 

 variations in the degree of aggregation from one mass to an- 

 other without affecting the mean state (per unit of volume). 



The case is comparable on smaller scale to the minute 

 masses (each consisting of a number of molecules aggregated 

 about a common centre) forming the compound molecules of 

 a gas of high complexity. Here it is a known fact that such 

 a velocity of translatory motion (dependent on temperature) 

 might be given to these minute masses (compound molecules) 

 composing the gas as to break them up into discrete mole- 

 cules. A less velocity than this is conceivable at which a 

 small degree of aggregation is possible, and a still less velocity 

 where a still greater degree of aggregation can ensue. Indeed, 

 if the constituents be numerous so as to admit of a great va- 

 riety of groupings, a very considerable range in the degree of 

 aggregation is possible by varying the rates of translatory 

 motion (dependent on varying temperatures). It is also a 

 recognized fact here that the degree of aggregation by any 

 given rate of translatory motion (temperature) refers only to 

 the mean state, and not to the state of each of the individual 



* It is evident that since we are not limited as to velocit}^ a certain 

 (adequate) velocity must exist, corresponding- to an adequate degree of 

 energy, that would suflice to produce this result. Of course the cubical 

 envelopes are merely used for facility of illustration, and may be supposed 

 abolished, substituting- for them infinite space containing- matter in a 

 similar state. 



