Dynamical Theory of Heat. 375 



I still adhere : I trust you find nothing in it which indicates a 

 desire on my part to question your claim to the honour of being 

 the experimental demonstrator of the equivalence of heat and 

 work." It was in the presence of this statement that you ven- 

 tured to insinuate in ' Good Words ' your charge of depreciation 

 and suppression ; and it is in the presence of this statement, 

 requoted for your especial information in the March Number of 

 the Philosophical Magazine, that you now dare to reiterate this 

 charge. The quotation from my book will be recognized by the 

 court before which you and I now stand, as springing from the 

 same spirit of goodwill towards Mr. Joule, and the same high 

 appreciation of his services which have marked all that I have 

 said and written regarding him. It is not only 'now 3 that I 

 entertain those feelings, as you intimate in your concluding pa- 

 ragraph, they have always been mine ; and they will continue to 

 be mine despite an advocacy on your part so unwise and so un- 

 warranted as to be well calculated to produce a reaction against 

 the man who is unfortunate enough to find in you the assertor 

 of his claims. 



Your article in 'Good Words ' was professedly written to 

 counteract the errors and absurdities of previous writers. " We 

 have aimed," you say, " at preparing an article which shall at 

 all events be accurate as far as human knowledge now reaches," 

 or as you more cuttingly express it in reference to my poor 

 lecture, you " seized the opportunity of distributing among its 

 [' Good Words '] 120,000 readers a corrective to the erroneous 

 information which you saw stealing upon them through the 

 medium of popular journals." Well, let us inquire a little into 

 the quality of the " corrective." In putting Mr. Joule forward 

 as the founder of the dynamical theory of heat, you write thus : — 

 "In 1843 he (Mr. Joule) published the results of a well-planned 

 and executed series of experiments, by which he ascertained that 

 a pound of water is raised one degree Fahrenheit in temperature 

 by 772 foot-pounds of mechanical work done upon it. In other 

 words, if a pound of water fall from a height of 772 feet, and 

 the kinetic energy thus acquired in the form of ordinary motion 

 be entirely transformed into the kinetic energy of heat, the 

 water will be one degree hotter than before its fall." You here 

 prove yourself to be as ill-informed regarding the labours of 

 Joule as you are regarding those of Mayer. It was in 1849, 

 and not in 1843, that Mr. Joule proved the mechanical equiva- 

 lent of heat to be 772 foot-pounds. His determinations of the 

 mechanical equivalent of heat, published in 1843, varied from 

 1040 to 587 foot-pounds. They were so discordant that nobody 

 attached any value to them. It was with reference to Mr. Joule's 

 earlier experiments that Helmholtz expressed himself thus, in 



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