GIBBS' PAPERS I AND II 



51 



of molecular motion, has made necessar}' and possible a new branch of 

 mechanics, under the name of thermo-dj'namics. This theory has not 

 only introduced new ideas into science, but has demanded the applica- 



FlG. 1 



Fig. 2 



Fig. 3 



Fig. 4 



The Thermodynamic Surface (Maxwell's Model) 



Fig. 1. Vertical axis; energy (e). Axis of volume (?0 toward the front 

 and left. Axis of entropy (tj) toward the right. 



Fig. 2. Vertical axis; energy (e). Axis of volume (r) toward the front 

 and right. Axis of entropy (77) toward the right and back. 



Fig. 3. Vertical axis; energy (e). Axis of volume (v) toward rear and 

 left. Axis of entropy (r/) toward front and left. 



Fig. 4. Vertical axis; volume {i'). Axis of entropy (rj) toward front 

 and left. Axis of energy (e) toward the right. 



tion, if not the invention, of special mathematical equations. Clausius 

 has devoted thirty j^ears to the develoi)ment of thermo-dynamics, and 

 at the end of his ninth memoir he expresses, in two brief sentences, the 



