56 WILSON 



ART. C 



alone any critique of its importance to science; the references 

 are to the previous state of thermodynamics and to the thermo- 

 dynamic surface and Maxwell's model of it, i.e., to material by 

 Gibbs contained in his Paper II, which we have been discussing. 

 It may be recalled that in December 1878, more than two years 

 prior to President Lovering's address, Gibbs had published in 

 the American Journal of Science an Abstract of his memoir 

 (Gibbs, I, Paper IV) from which certain important descriptive 

 material might have been culled more readily than from the 

 original. That the Rumford Committee realized that a great 

 contribution had been made by Gibbs and that they promptly 

 recognized it by their recommendation of the award of the medal 

 is clear, but in how far they appreciated the nature and signifi- 

 cance of the contribution is not indicated.* 



Particularly interesting in the reply by Gibbs is his reference 

 to the fact that it is only for gases that he has been able to write 

 the equation expressing the thermodynamic functions for a body 

 of variable composition. Perhaps his great attention in his 

 course to van der Waals' equation was because, although its 

 accuracy for liquid and vapor phases is not so great as that of 

 the gas equation for gases, it offered some fair approximation to 

 the representation of a decidedly less restricted state of matter 

 and led to equations expressing the thermodynamic functions 

 for more general bodies of variable composition. It is custom- 

 ary for the recipient of the medal to make a considerable address 

 expounding as well as he can to a general academic audience the 

 significance of some of his contributions. What would Gibbs 

 have said about the memoir on Heterogeneous Equilibrium had 

 he been able to be present? Would he have alluded to some of 

 the important possible applications of his work on osmotic equi- 

 librium or to the significance of his phase rule (obviously a 

 matter easy to make graphic to the kind of audience he would 



* In the first footnote of the Abstract (Gibbs, I, p. 358) Gibbs points 

 out that Massieu "appears to have been the first to solve the prob- 

 lem of representing all properties of a body of invariable composition 

 which are concerned in reversible processes by means of a single func- 

 tion" — a fact that was probably unknown to him at the time of printing 

 Paper II. 



