A KINETIC THEORY OF MATTER. 229 



figuration of motion in a continuous all-pervading 

 liquid. I do not myself see how we can ever 

 permanently rest anywhere short of this last 

 view ; but it would be a very pleasant temporary 

 resting-place on the way to it, if we could, as it 

 were, make a mechanical model of a gas out of 

 little pieces of round, perfectly elastic solid 

 matter, flying about through the space occupied 

 by the gas, and colliding with one another and 

 against the sides of the containing vessel. This 

 is, in fact, all we have of kinetic theory of gases 

 up to the present time, and this has done for 

 us, in the hands of Clausius and Maxwell, the 

 great things which constitute our first step to- 

 wards a molecular theory of matter. Of course 

 from it we should have to go on to find an 

 explanation of the elasticity and all the other 

 properties of the molecules themselves, a subject 

 vastly more complex and difficult than the 

 gaseous properties for the explanation of which 

 we assume the elastic molecule ; but without any 

 explanation of the properties of the molecule 

 itself, with merely the assumption that the mole- 



