Josiah Willard Gibhs. 191 



head of tlie third paper the author puts the famous statement 

 of Clausius : "Die Energie der Welt ist constant. Die Entropie 

 der Welt strebt einem Maximum zu." He proceeds to show 

 that the above condition for equilibrium, derived from the two 

 laws of thermodynamics, is of universal application, carefully 

 removing one restriction after another, the first to go being 

 that the substance shall be chemically homogeneous. The 

 important analytical step is taken of introducing, as variables 

 in the fundamental differential equation, the masses of the 

 constituents of the heterogeneous body ; the differential coef- 

 ficients of the energy with respect to these masses are shown 

 to enter the conditions of equilibrium in a manner entirely 

 analogous to the " intensities," pressure and temperature, and 

 these coefficients are called potentials. Constant use is made 

 of the analogies with the equations for homogeneous sub- 

 stances, and the analytical processes are like those which a 

 geometel* would use in extending to ?i-dimensions the geome- 

 try of three. 



It is quite out of the question to give, in brief compass, 

 anything approaching an adequate outline of this remarkable 

 work. It is universally recognized that its publication was an 

 event of the first importance in the history of chemistry, that 

 in fact it founded a new department of chemical science 

 which, in the words of M. Le Chatelier, is becoming compar- 

 able in importance with that created by Lavoisier. Neverthe- 

 less it was a number of years before its value was generally 

 known ; this delay was due largely to the fact that its 

 mathematical form and rigorous deductive processes make it 

 difficult reading for any one, and especially so for students of 

 experimental chemistry whom it most concerns ; twenty-five 

 years ago there was relatively only a small number of chemists 

 who possessed sufficient mathematical knowledge to read easily 

 even the simpler portions of the paper. Thus it came about 

 that a number of natural laws of great importance which were, 

 for the first time, clearly stated in this paper were subse- 

 quently, during its period of neglect, discovered by others, 

 sometimes from theoretical considerations, but more often by 

 experiment. At the present time, however, the great value 

 of its methods and results are fully recognized by all students 

 of physical chemistry. It was translated into German in 1891 

 by Professor Ostwald and into French in 1899 by Professor 

 Le Chatelier ; and, although so many 3^ears had passed since 

 its original publication, in both cases the distinguished trans- 

 lators give, as their principal reason for undertaking the task, 

 not the historical interest of the memoir, but the many 

 important questions which it discusses and which have not 

 even yet been worked out experimentally. Many of its 



