LOW-TEMPERATURE RESEARCHES 



brations, is elastic, tending to be thrown back from 

 every other molecule with which it comes in contact, 

 just as a vibrating tuning-fork kicks itself away from 

 anything it touches. And of course the vigor of the 

 recoil will depend upon the vigor of the vibration and 

 the previous movements. But since these movements 

 constitute temperature, this is another way of saying 

 that the higher the temperature of a body the more its 

 molecules will tend to spring asunder, such separation 

 in the aggregate constituting expansion of the mass 

 as a whole. Thus the familiar fact of expansion of a 

 body under increased temperature is explained. 



But now, since all molecules are vibrating, and so 

 tending to separate, it is clear that no unconfined mass 

 of molecules would long remain in contiguity unless 

 some counter influence tended to draw them together. 

 Such a counter influence in fact exists, and is termed 

 the "force" of cohesion. This force is a veritable 

 gravitation influence, drawing every molecule towards 

 every other molecule. Possibly it is identical with 

 gravitation. It seems subject to some law of de- 

 creasing in power with the square of the distance ; or, 

 at any rate, it clearly becomes less potent as the dis- 

 tance through which it operates increases. 



Now, between this force of cohesion which tends to 

 draw the molecules together, and the heat vibrations 

 which tend to throw the molecules farther asunder, 

 there seems to be an incessant battle. If cohesion pre- 

 vails, the molecules are held for the time into a relative- 

 ly fixed system, which we term the solid state. If the 

 two forces about balance each other, the molecules 

 move among themselves more freely but maintain an 



VOL. V. 4 4Q 



