Kinetic Interpretation of the Dissipation Function. 455 



Between each grain and its neighbours there is a true 

 surface, the tension of which probably depends in some 

 measure upon the relationship of their axes to each other. 



Now Ave know that a by no means unimportant portion of 

 the energy of a solid body depends upon its surface area ; 

 and I would suggest also that it depends in some measure 

 upon the surfaces separating the crystal units, of which it is 

 composed, from each other, even when they are of similar 

 composition. 



In a block of glacier-ice, therefore, or in a block of granite, 

 the total energy depends, not only upon its temperature and 

 volume, but also upon the energy of the surface-tensions of 

 its component grains, whether they be similar or dissimilar 

 in composition. 



Now it is an important theorem of Dynamics that, for the 

 stable equilibrium of a system, the potential energy of the 

 whole must be a minimum. For instance, when immiscible 

 liquids are intimately mixed, work is done in increasing their 

 surface-energy, and the energy thus rendered potential serves 

 to again separate them. Glacier-ice is in much the same 

 condition. Its potential energy is always tending to a 

 minimum, a condition which can only be reached by the 

 disappearance of the interfaces between the crystal-grains. 

 Being viscous, it is unable to do more than delay the dis- 

 appearance of the interfaces, and the grains would continue 

 to grow larger and larger with the lapse of time were it not 

 for the fact that they are broken in the production of the 

 ribboned or veined structure. 



For the same reason masses of all liquids possessing struc- 

 ture, whatever their viscosities may be, eventually become 

 single crystalline particles. 



Yours truly, 



R. M. Deeley. 



XLV. On the Kinetic Interpretation of the Dissipation 

 Function. By Dr. Ladislas Natanson, Professor of 

 Natural Philosophy, University of Cracow*. 



1. "|"N the following paper we consider a fluid medium from 

 JL Maxwell's point of view (see the paper " On the 

 Dynamical Theory of Gases," i Scientific Papers,' ii. 26) ; 

 we suppose it to be composed of a great number of moving 

 molecules. Let f, 77, f be the components of the individual 

 (or " molecular ;; ) velocity of a molecule ; and let u, v, w be 



* Translated from " Rozprawy " (Transactions) of the Cracow Academy 

 of Sciences, Math, and Phys. Section, vol. xxix. Communicated by the 

 Author. 



2H2 



