60 PROCEEDINGS OF THE AMERICAN ACADEMY. 



other its capacity.* Thus, for example, pressure, surface tension, elec- 

 trical, potential, and temperature are considered to be the intensities 

 concerned in energy changes in which the corresponding capacities are 

 respectively volume, surface, quantity of electricity, and entropy. We 

 may denote in general the intensity of any energy by /and its capacity 

 by H. If vre substitute / and H for T'aud S in equation (16) and for 

 Pand V in (17), the equations become identical except for the minus sign 

 in (16). We are thus led to suspect the existence of a general equation 

 of the form 



<A2 



H. - H^ ('«) 



a 1 y jtpi . 

 and further, of the equation for a single phase, 



This equation would mean that if the fugacity is a function of a number 

 of energy intensities, /, /', /", etc., the rate of change in the quaiitity 

 R Tlnij/, with a change in one of the intensities alone, is equal to the 

 corresponding capacity. In other words, this equation, if true, expresses 

 a law so far reaching that it embraces every possibility of the change of 

 state of any simple substance under all conceivable conditions. Let us 

 examine the validity of this equation for all cases in which the escaping 

 tendency can be shown to be influenced by the intensities of various 

 energies. 



The influence of pressure is given in equation (14), which may be 

 written, 



and therefore conforms to equation (19). 



* These quantities have been hitherto called the factors of energy, and their 

 product has been written equal to the quantity of energy concerned. I believe 

 that this part of the theory is absolutely unjustified by the facts, and that it has 

 been the chief cause of the hostility which has been shown to a conception which 

 is valuable in research and has proved a veritable boon in the pedagogical treat- 

 ment of energetics. I hope soon in another paper to discuss this whole question, 

 especially in the light of the results of the present paper. Meanwhile we may 

 speak of intensity and capacity as the dimensions of energy, signifying that their 

 product has the dimensions of energy. 



