348 Sir W. Thomson on Thermodynamic Motivity. 



Theory of Heat," published in the Transactions of the Royal 

 Society of Edinburgh for May 1854, and in the Philosophical 

 Magazine for 1855, first half-year, the formula 



t -f- t , -t-... -t- ^_ 1} -r- <(B) -u 

 is given as an equivalent for 



which was first published in the Proceedings of the Royal 

 Society of Edinburgh for 1851, and Phil. Mag. 1852, first 

 half-year. Tait had actually quoted the formula from my 

 1854 paper in § 176 of his book, and so left absolutely no 

 foundation for Professor Clausius' objection to his saying 

 " This is Thomson's expression &c," quoted in his letter above. 



As to the l Good Words ' article on Energy which appeared 

 under our joint names, Professor Tait and I are equally 

 responsible for its contents. I claim my full share of the 

 " scientific patriotism " commended in that article, and cannot 

 assent to Professor Clausius' giving all the credit of it to Pro- 

 fessor Tait. 



In compliance with the concluding sentence of Professor 

 Tait's letter, I hope in the course of a few days to write out, 

 and send to the Philosophical Magazine for publication, a short 

 statement of the communication on Thermodynamic Motivity 

 which I made viva voce to the Royal Society of Edinburgh on 

 April 3rd, 1876. 



LV. On Thermodynamic Motivity. 

 By Sir W. Thomson, F.R.S.* 



AFTER having for some years felt with Professor Tait the 

 want of a word " to express the Availability for work 

 " of the heat in a given magazine, a term for that possession 

 " the waste of which is called Dissipation" f , I suggested three 

 years ago the word Motivity to supply this want, and made a 

 verbal communication to the Royal Society of Edinburgh de- 

 fining and illustrating the application of the word ; but as the 

 communication was not given in writing, only the title of the 

 paper, "Thermodynamic Motivity," was published. In con- 

 sequence of Professor Tait's letter to me, published in the 

 present Number of the Philosophical Magazine, I now offer, 



* Communicated by the Author. 



t Tait's ' Thermodynamics/ first edition (1868), § 178 : quoted also 

 in Professor Tait's letter in the present Number of the Philosophical 

 Magazine. 



