52 WILSON ART. c 



fundamental laws of the universe which correspond to the two funda- 

 mental theorems of the mechanical theory of heat : 1 . The energy of the 

 universe is constant; 2. The entropy of the universe tends towards a 

 maximum. 



"Professor J. Willard Gibbs, in his discussion of the 'Equilibrium of 

 Heterogeneous Sul)stances/ derives his criteria of efiuilibrium and sta- 

 bility from these two theorems of Clausius, and places the two generali- 

 zations of Clausius in regard to energy and entropj' at the head of his 

 first publication. Having derived from his criteria some leading equa- 

 tions, and having defined his sense of 'homogeneous' and its opposite, 

 he applies these equations: — 



"1. To the internal stabilitj^ of homogeneous fluids. 



"2. To heterogeneous masses, under the influence of gravity or other- 

 wise; such as gas-mixtures, solids in contact with fluids, osmotic forces, 

 capillarity, and liquid films. 



"3. Finally, he considers the modifications introduced into the con- 

 ditions of equilibrium by electromotive forces. 



"His treatment of the subject is severely mathematical, and incap- 

 able of being translated into common language. The formulas, how- 

 ever, are not barren abstractions, l)ut have a physical meaning. 



"The laws of thermo-dynamics reach down to the heart of physics 

 and extend tlieir roots in all directions. It is now understood that the 

 energy of a system of bodies depends on the temperature and physical 

 state, as well as on the forms, motions, and relative positions of these 

 bodies. The Rumford Committee congratulate the Academy on the 

 opportunity they now enjoy of awarding the Rumford Premium for a 

 contribution to physical science of far-reaching importance; not antici- 

 pating, but already realizing, the approval which this award must 

 receive from all who are conversant with the subject. 



"For the Committee, 



"Joseph Lovering, ChairmanJ' 



The medal was awarded at the meeting of January 12, 1881, 

 Professor Lovering having in the interim been elected president 

 of the Academy. His address as Chairman of the Committee 

 was in part* as follows. 



"On the mechanical theory of heat, as a foundation, has been erected 



* The material here quoted is from Proc. Amer. Acad. Arts Sci., 16, 

 pp. 407-408 and 417-421. The introductory portion which deals with 

 the history of the award is omitted. 



