222 PETER GUTHRIE TAIT 



of disgregation in which one becomes conscious of the increase of the general sum 

 of Entropy. Meanwhile till 



Ergal and Virial from their throne be cast 

 And end their strife with suicidal yell 



I remain, Yrs. -." 

 at 



In a letter of date Oct. 13, 1876, Maxwell made clearer references to 

 the point at issue between Tail and Clausius, and gave at the same time 

 some interesting confessions as to his own knowledge or, rather, ignorance 

 of the subject. He wrote : 



" When you wrote the Sketch your knowledge of Clausius was somewhat defective. 

 Mine is still, though I have spent much labour upon him and have occasionally been 

 rewarded, e.g., earlier papers, molecular slotting 1 , electrolysis, entropy, and concentra- 

 tion of rays.... 



" N.B. In the latter paper the name of Hamilton does not occur. When you are 

 a-trouncing him, trounce him for that. Only perhaps Kirchhoff ignored Hamilton first 

 and Clausius followed him unwittingly not being a constant reader of the R. I. A. 

 Transactions, and knowing nothing of H. except (lately) his Princip., which he and 

 others try to degrade into the 2nd law of A as if any pure dynamical statement 

 would submit to such an indignity. 



"With respect to your citation of Thomson it would need to be more explicit. 

 The likest thing I find to what you give is in the ist paper on D. T. of H. 

 (17 March, 1851, p. 272 & 273), but I do not find dq divided by anything like t. 



" I think Rankine, by introducing his thermodynamic function <f> which is Jdg/t, made 

 a great hit, because <f> is a real quantity whereas q is not, only dq = td$. There are 

 many things in T which are equivalent to this because T has worked at the same 

 subject and worked correctly and all mathematical truth is one, but you cannot expect 

 Clausius to see this unless it stands very plain in print. In short Rankine's state- 

 ments are identical with those of C, but T's are only equivalent... 



" With respect to our knowledge of the condition of energy within a body, both 

 Rankine and Clausius pretend to know something about it. We certainly know how 

 much goes in and comes out and we know whether at entrance or exit it is in the 

 form of heat or work, but what disguise it assumes when in the privacy of bodies, 

 or, as Torricelli says, " nell' intima corpulenza de' solide naturali," is known only to 

 R., C. and Co." 



The paper mentioned by Maxwell was not, however, the paper referred 

 to by Tail, as will appear immediately. 



Among Tail's correspondence an interesting letter from Thomson (Kelvin) 



1 Stot, a Scottish word meaning to impinge and rebound, still in constant use among 

 school children of all classes, e.g., to slot a ball. Compare German slossen. 



