Prof. Tyndall on the Claims of Mayer and Joule. 223 



the spring of last year, the name and merits of Mr. Joule were 

 constantly before my audience ; and throughout the entire course 

 I made but a single passing allusion to Mayer. In fact, I was 

 then as unacquainted with the real merits of Mayer as Professors 

 Thomson arid Tait appear to be now*. But even after I had 

 made myself acquainted with all that Mayer had done, I did not 

 bate a jot in my admiration of Mr. Joule. For a whole month 

 before the above words regarding depreciation and suppression 

 received public utterance, the following passage, with reference 

 to the mechanical theory of heat, stood in the largest type of 

 the Philosophical Magazine : — " It is to Mr. Joule, of Man- 

 chester, that we are almost wholly indebted for the experimental 

 treatment of this subject. With his mind firmly fixed upon a 

 principle, and undismayed by the coolness with which his first 

 labours appear to have been received, he persisted for years in 

 his attempts to prove the invariability of the relation between 

 heat and ordinary mechanical force. He placed water in a 

 suitable vessel, agitated it by paddles moved by measurable 

 forces, and determined the elevation of temperature ; he did the 

 same with mercury and sperm-oil. He also caused discs of 

 cast iron to rotate against each other, and measured the heat 

 produced by their friction. He urged water through capillary 

 tubes, and measured the heat thus generated. The results of 

 his experiments leave no doubt upon the mind, that under all 

 circumstances the absolute amount of heat produced by the ex- 

 penditure of a definite amount of mechanical force is fixed and 

 invariable." 



In my '. Lectures on Heat, considered as a Mode of Motion/ 

 now on the point of publication, I have drawn the following 

 parallel between Joule and Mayer : — 



"Do I refer to these things in order to exalt Mayer at the 

 expense of Joule ? It is far from my intention to do so. The 

 man who through long years, without encouragement, and in 

 the face of difficulties which might well be deemed insurmount- 

 able, could work with such unswerving steadfastness of purpose 

 to so triumphant an issue, is safe from depreciation. And it is 

 not the experiments alone, but the spirit which they incorporate, 

 and the applications which their author made of them, which 

 entitle Mr. Joule to a place in the foremost rank of physical 

 philosophers. Mayer's labours have, in some measure, the 

 stamp of a profound intuition, which rose, however, to the 

 energy of undoubting conviction in the author's mind. Joule's 

 labours, on the contrary, are an experimental demonstration. 

 True to the speculative instinct of his country, Mayer drew 

 large and weighty conclusions from slender premises, while the 



* I here, of course, refer to the time when they wrote their article. 



