46 Prof. Tyndall's Notes on Scientific History. 



pier combinations. They therefore consume a quantity of chemi- 

 cal forces, and generate in their place heat and mechanical forces. 

 As the last represent a comparatively small amount of work in 

 comparison with the amount of heat, the question of the con- 

 servation of force reduces itself to this : — Do the combustion and 

 the change of materials in the nutriment generate an equal 

 quantity of heat to that yielded up by the animal ? According 

 to the experiments of Dulong and Despretz, this question can, at 

 least approximately, be answered in the affirmative." 



54. Helmholtz made this statement independently of Mayer, 

 for when he wrote he did not know what had been published two 

 years before at Heilbronn * ; and clearly as the above paragraph 

 illustrates his insight on this momentous point, it could not be 

 accepted as an adequate abstract of Mayer's previous writings 

 on the same subject. In a lecture of varied excellence, trans- 

 lated by myself, and published in the Philosophical Magazine, 

 1856, vol. ii., Helmholtz expresses in clear and beautiful lan- 

 guage the relation of animals to vegetables, and of both to the 

 sun. The lecture was given at Konigsberg on the 7th of Fe- 

 bruary 1854; and if the reader wishes to realize fully the extent 

 to which Mayer had occupied this field, and the scantiness of 

 the additions made to our knowledge of vital dynamics during 

 the nine years following the publication of Mayer's essay, he may 

 compare pp. 509, 510, and 511 of Helmholtz's lecture with sec- 

 tions 4, 5, 6, and 7 of this resume. 



55. One word more on this subject, which shall have as slight 

 a personal tinge as I can under the circumstances impart to it. 

 In a religious periodical, which we are informed numbers 120,000 

 readers, Prof. Thomson undertook to give an accurate account of 

 the discovery, nature, and development of the law of the conserva- 

 tion of energy, professedly with the view of correcting the errors 

 which he believed me to be disseminating regarding Mayer. In 

 that article he charged me with depreciation and suppression, 

 and these bad words rest un retracted in the pages of ' Good 

 Words' to this hour. After dealing with various questions 

 relating to the " conservation of energy," Prof. Thomson comes 

 at length to the " grandest question of all," and states it 

 thus : — " "Whence do we derive the stores of potential energy 

 which we employ as fuel and food? What produces the 

 potential energy of a loaf or a beefsteak ? What supplies the 

 coal and the water power, without which our factories would 

 stop ? " And the answer to this question is " the sun." Prof. 

 Thomson can now name the man who answered this question 

 seventeen years before he called it the grandest of all — the man 



* " I mj'self, without being acquainted with either Mayer or Colding," 

 &c— Phil. Mag. S. 4. vol. ii. p. 409. 



