346 Prof. P. G. Tait on the Dissipation of Energy. 



on your papers, mainly because they appeared to me to be 

 greatly superior to all others on the subject in the three very 

 important qualities of simplicity, conciseness, and freedom 

 from hypothesis, I am anxious to know whether the above 

 passage meets with your approval. 



From Prof. Clausius's comments it appears, as I have 

 already said, that he considers the method I have adopted 

 from you to be one which cannot be applied except to re- 

 versible cycles, and which, therefore, it is absurd to employ 

 in any argument connected with dissipation of energy. 



Prof. Clausius also disputes the correctness of my reference 

 to your paper in the Philosophical Magazine, as containing 

 the above expression for the heat dissipated. You ought to 

 be a competent authority on such a question as this. 



I do not now reply to the many other remarks of Prof. 

 Clausius, simply because they refer to myself, my motives, 

 and my book, and not to the principles or the history of 

 science. As the matter affects you, however, I may mention 

 that Professor Clausius attributes to me the real authorship of 

 the paper on "Energy" which we jointly wrote for i Good 

 Words,' and which has been often referred to in the Philoso- 

 phical Magazine. 



But the passage in brackets in the extract above indicates a 

 want of proper nomenclature, which would, I think, be well 

 met by the publication of the paper on Thermodynamic Mo- 

 tivity, read by you some years ago to the Royal Society of 

 Edinburgh. 



Yours truly, 



38 George Square, Edinburgh, P. G. TAIT. 



March 17th, 1879. 



Note by Sir W. Thomson on the 'preceding Letter. 



The passage quoted, with amendments, by Professor Tait 

 from his ' Thermodynamics,' seems to me perfectly clear and 

 accurate. Taken in connexion with the sections which pre- 

 ceded it in the original, its meaning was unmistakable ; and 

 a careful reader could have found little or no difficulty in 

 making for himself the necessary corrections with which Pro- 

 fessor Tait now presents it. It is certainly not confined to 

 reversible cycles; but, on the contrary, it gives an explicit 

 expression for the amount of energy dissipated, or, as I put it, 

 " absolutely and irrecoverably wasted " in operations ^ of an 

 irreversible character. My original article " On a Universal 

 Tendency in Nature to the Dissipation of Mechanical Energy," 



