50 WILSON 



ART. 



III. Further Notes on Gibbs' Lectures. Photographs of 

 Models of the Thermodynamic Surface 



These thirty lectures as given in the academic year 1899-1900 

 represent the development, discussion, and application of the 

 matter in Papers I and II so far as Gibbs covered it. In the 

 year 1901-1902 he covered the same ground in just fifteen lec- 

 tures. He continued with a lecture on dynamical similarity 

 and the theory of models which he applied to the consideration 

 of intermolecular forces and the problem of corresponding states, 

 and then launched into the topic of heterogeneous substances 

 (Paper III). It will be seen that although he laid great stress on 

 the physical and on the logical aspects of thermodynamics, and 

 spent a good deal of time on van der Waals' equation as a type 

 of equation of state, he did not indulge in many numerical appli- 

 cations, nor discuss practical engineering consequences of the 

 theory. He used chiefly the pt-diagram, giving scant mention 

 to the temperature entropy diagram. 



An interesting and helpful episode in the course was the illus- 

 tration of the discussion of the thermodynamic surface by a 

 model of the surface for water, which had been sent him by 

 Maxwell. Four photographs of this model taken from different 

 points of view are reproduced here. The legends indicate the 

 direction of the axes. 



Maxwell's highly favorable comments on the work of Gibbs and 

 the concrete evidence which he gave of his opinion through the 

 construction of the model of the thermodynamic surface prob- 

 ably did more at the time to convince physicists of the impor- 

 tance of Gibbs's contributions than the reading of so long, so 

 novel, so closely reasoned and withal so difficult a memoir as 

 that on Heterogeneous Equilibrium. It is of interest in this 

 connection to give the record of the award by the American 

 Academy of Arts and Sciences of its Rumford Medal to Gibbs. 

 At the meeting of May 25, 1880, Professor Lovering presented 

 the following report from the Rumford Committee.* 



"The mechanical theory of heat, which treats of heat as being, not a 

 pecular kind of matter called caloric, but as being some form or forms 



* The Committee consisted of Wolcott Gibbs, E. C. Pickering, J, M. 

 Ordway, John Trowbridge, J. P. Cooke, Joseph Lovering, G. B. Clark. 



