^, , XI. 0^ the Mechanical Theonj of Heatl^'^ ^^^^j! 



,., . % W. J. Macquorn Rankine, F.KS.E. &•» ' <**^*'^* 



^J, 'To Me Editors of the Philosophical Maaazine and Journah ^^ 



A S you have announced your intention to publish a translation 

 •^^ of the memoir of M. Clausius on the mechanical agency 

 of heat, which appeared last summer in PoggendorfF^s^ww«7ew_, 

 I beg leave to offer to you the English version of a letter on the 

 subject of the First Part of M. Clausius^s paper, which was ad- 

 dressed by me to the editor of that journal, and published in the 

 9th Number for 1850. 



JUnoqri I am, Gentlemen, 'r// 



Your most obedient Servant, { 



W. J. Macquorn Rankine;~~ 

 30 Great George Street, Westminster, February 11, 1851. 



Letter from Mr. Macquorn Rankine to Dr. J. C. Poggendorff*. 



Having observed in your Annalen der Physik und Chemie for 

 April 1850 a very able and interesting paper on the motive power 

 of heat, by M. Clausius, 1 beg leave to call your attention to a 

 paper which was presented by me to the Royal Society of Edin- 

 burgh in October 1849, read on the 4th of February 1850, and 

 published in the 20th volume of their Transactions, Part First ; in 

 which paper, among other results, I have arrived at conclusions 

 respecting the specific heat of gases and vapours, and the latent 

 heat of evaporation, agreeing with those of M. Clausius, and de- 

 duced from principles, and by means of a method, which, though 

 differing in some details from those employed by him, are the 

 same in their essential points. In doing, so, I have no wish to 

 detract from the merit of M. Clausius, or to establish any rivalry 

 bet weep him and myself; on the contrary, I am gratified to find 

 the results of my investigations confirmed by so eminent an 

 authority. 



It is probable that you have had, or will soon have, an oppor- 

 tunity of seeing the part of the Edinburgh Transactions to which 

 I refer; should that not be case, however, I shall be glad to 

 send you a copy of the paper as soon as I am aware of a conve- 

 nient and secure means of conveyance. In the meanwhile I 

 shall give you a summary of its contents. t ,'yiBW ii Yi 



It consists of an introduction and four sections. 



The introduction explains the general principles of a conjecture 



* From Poggendorff 's Annalen der Physik und Chemie for 1850, No, 9. 



