

Prof. TyndalPs Notes on Scientific History. 43 



IX. 



49. There are a few points remaining, which, to preserve the 

 events of scientific history in their true relationship, ought to be 

 referred to here. It has been asserted mildly (as is his wont) 

 by Mr. Joule, less mildly (as is their wont) by his northern sup- 

 porters, that, as regards vital dynamics, he anticipated Mayer 

 by two years. In a letter published in the Philosophical Maga- 

 zine for August 1862, Mr. Joule writes thus : — "Permit me to 

 remark, that I applied the dynamical theory of heat to vital pro- 

 cesses in 1843." Let all justice be done to Mr. Joule regarding 

 his application of the theory. In a postscript to a paper in the 

 December Number of the Philosophical Magazine for 1843 he 

 writes thus : — 



50. " On conversing a few days ago with my friend Mr. John 

 Davies, he told me that he had himself a few years ago at- 

 tempted to account for that part of animal heat which Craw- 

 ford's theory had left unexplained, by the friction of the blood 

 in the veins and arteries, but that, finding a similar hypothesis 

 in Haller's ' Physiology/ he had not pursued the subject further. 

 It is unquestionable that heat is produced by such friction, but 

 it must be understood that the mechanical force expended in 

 the friction is a part of the force of affinity, which causes the 

 venous blood to unite with the oxygen, so that the whole heat 

 of the system must still be referred to the chemical changes. 

 But if the animal were engaged in turning a piece of machinery, 

 or in ascending a mountain, I apprehend that, in proportion to 

 the muscular effort put forth for the purpose, a diminution of 

 the heat evolved in the system by a given chemical action would 

 be experienced." 



This citation embraces, I believe, every word that was written 

 on " vital dynamics " by Mr. Joule, before the appearance of 

 Mayer's paper on organic motion. It consists of a conjecture, the 

 sagacity of which is in accordance with the insight always mani- 

 fested by Mr. Joule. Let the reader compare it with sections 

 4 to 7 of this resume, and make the deductions which he deems 

 right from his estimate of Mayer's work. 



51. In 1852 Prof. Wm. Thomson wrote on the subject of " vital 

 dynamics," and it will be instructive to compare what he has 

 done with what had been done by Mayer seven years earlier. 



enabling him to see clearly the bearing of such facts as he possessed. 

 They enabled him to think out the law of conservation, and his conclusions 

 received the stamp of certainty from the subsequent experimental labours 

 of Mr. Joule. In reference to their comparative merits, I would say that, 

 as Seer and Generalizer, Mayer, in my opinion, stands first, — as Experi- 

 mental Philosopher, Joule. 



