374 Prof. Tyndall's Remarks on the 



many a paper by Mayer, of Heilbronn. Its title is ' Bemerkungen 

 uber die Krafte der unbelebten Natur/ and its date is 1842/' 

 Would you have the goodness to point out a single word regard- 

 ing the mechanical value of heat, or the mechanical equivalent of 

 heat in any of Mr. Joule's writings prior to the month of Decem- 

 ber 1843 ? If no such word occurs, if Helmholtz and Verdet be 

 correct in assigning this date to the earliest experiments of Mr. 

 Joule on the ' Mechanical Value of Heat/ how am I to characterize 

 your statement that it was while Joule was pursuing and pub- 

 lishing his investigations that Mayer's paper, dated May 1842, 

 appeared ? If you should urge that these investigations led Mr. 

 Joule to his experiments on the mechanical equivalent of heat, 

 you simply repeat what I have myself stated in the very lecture 

 which has been the object of your unwarrantable attack. 



With reference to the manner in which I have met your insi- 

 nuations in my brief communication to the Philosophical Maga- 

 zine, we have the following remarks : — u I am unwilling to enter 

 upon matters of a more personal character, but it is impossible 

 to pass over the fact that, in answer to an expostulation from 

 Joule (having reference to this lecture), Prof. Tyndall referred 

 (Phil. Mag. 1862, second half year, p. 173) to statements which he 

 had made in a course of lectures which, he now tells us, were com- 

 pleted before he acquired those views of Mayer's claims to which 

 Joule so naturally objected, and that he now replies to Prof. 

 Thomson and me, not by showing that his lecture, to which we 

 referred, was free from the objections which we urged against it, 

 but by showing that these objections could not be urged against 

 a certain statement which he quotes from a work, not published, 

 but promised for publication." This reads smart ; but my frame 

 of mind disqualifies me from meeting it with mere smartness. 

 In replying to it I do not forget that my aim must not be to 

 satisfy you as to the uprightness of my course of action, but to 

 enable the scientific public to judge between your actions and 

 mine. On my return from Switzerland in 1862, I became 

 acquainted with the "expostulation" to which you refer; and I 

 also found waiting for me a private letter from Mr. Joule, remind- 

 ing me of what he had done in connexion with this subject. In 

 one of my morning lectures given six months previously, I had 

 recognized in the strongest terms the claims of Mr. Joule on the 

 very points to which, in his private note, he had directed my 

 attention. In my answer to his " expostulation " I quoted this 

 lecture, not expecting that Mr. Joule ought to be satisfied with 

 a statement made six months before, but for the purpose of 

 publicly renewing the value of that statement by resubscription 

 to it. This was done in the following words addressed to Mr. 

 Joule : — " Such has been my language regarding you, and to.it 



