586 



SCIENCE 



[N. S. Vol. XLHI. No. 1113 



Though he insists that Faraday's meth- 

 ods were mathematical, merely expressed in 

 symhols different from those "usual among 

 other mathematicians, yet the world knows 

 that Faraday's labors could not have borne 

 such abundant fruit, had there been no 

 Maxwell to interpret and push to their limit 

 his theories. By the combined labors of 

 physicist and mathematician it was finally 

 established that electro-magnetic action at 

 a distance is due to disturbances of the same 

 ether which conveys light-waves, and that 

 this action occupies measurable time; that 

 its velocity is indeed that of light itself, 

 and that light-<waves are of the same nature 

 as those sent out from an electric current 

 periodically interrupted. Compare this 

 certainty with the state of doubt, at the 

 beginning of the nineteenth century, upon 

 the relative merits of the corpuscular theory 

 and the undulation theory of light. Re- 

 fined measurement and rigorous logic had 

 indeed produced a visible effect ! 



In 1873 was published Maxwell's immor- 

 tal treatise on "Electricity and Magnet- 

 ism. ' ' In the same year appeared the first 

 work of Josiah Willard Gibbs, then a 

 young professor of mathematical physics in 

 Yale College, on "Graphical Methods in 

 the Thermodynamics of Fluids"; and only 

 five years later his most important work, 

 "On the Equilibrium of Heterogeneous 

 Substances. ' ' By this time the great law of 

 the conservation of energy was fully recog- 

 nized, but its detailed implications were 

 mostly still vague and imperfect. It was 

 certain, however, that in each conversion 

 of energy into other forms there was a deg- 

 radation of a part : that not all the energy 

 present could ever be utilized as mechanical 

 force; some small percentage was always 

 reserved in the form of heat, or electric 

 potential, or chemical energy, or otherwise. 

 Some vaguely understood quantity called 

 entropy was in the field, so that the total 



of energy present was divided between 

 entropy and free or available energy. 

 Gibbs set himself the problem: Given all 

 the masses and energies present, of every 

 particular kind, in a physical event, to 

 specify the amount of each kind that will 

 be present when equilibrium is restored. 

 In short, he wished to express as precisely 

 measured quantities the facts implied in 

 the conservation theory. As a corollary, he 

 verifies the brilliant dictum of Clausius, 

 that entropy is a continually increasiag 

 quantity. 



There is evidence that Maxwell's work 

 waited fifteen years for its full effect to be 

 felt in the scientific world. Gibbs 's researches 

 and theories waited somewhat longer, but 

 are now recognized quite generally (I 

 quote his biographer) as being "among 

 the greatest and most enduring monuments 

 of the wonderful scientific activity of the 

 nineteenth century." One may say in 

 brief that Gibbs passed from known laws 

 of physical and chemical action in infinites- 

 imal regions, to reach the succession of 

 transient conditions and to describe the 

 limiting condition of equilibrium, toward 

 which the total finite mass must tend — a 

 maximum of entropy, a minimum of free 

 energy. It is certainly plausible to say 

 that as he dealt with infinite systems, vary- 

 ing from point to point as well as in time, 

 he was forced to invent statistical methods 

 and to rely upon the theory of probability. 

 The most remarkable feature of his work 

 was the fact, noted by his French and Ger- 

 man translators and editors, that its the- 

 orems reached beyond truth as experi- 

 mentally known, and served as guides for 

 laboratory research. To paraphrase his 

 biographer, the important and admirable 

 thing in his work is not any new physical 

 hypothesis, but the extraordinary mathe- 

 matical power which deals simply and 

 rigorously with relations of great apparent 



