1 862.] Professor Tt/ndall on Force. 535 



and all that I liave said on this subject has been derived from him. 

 Wlien we consider the circumstances of Mayer's life, and the period at 

 which he wrote, we cannot fail to be struck m ith astonishment at what 

 he has accomplished. Here was a man of genius workin<^ in silence, 

 animated solely by a love of his subject, and arriving at the most im- 

 portant results, some time in advance of those whose lives were entirely 

 devoted to Natural Philosophy. It was the accident of bleeding a 

 feverish patient at Java in 1840 that led Mayer to speculate on these 

 subjects. He noticed that the venous blood in the tropics was of a 

 much brighter red than in colder latitudes, and his reasoning on this 

 fact led liim into the laboratory of natural forces, where he has worked 

 with such signal ability and success. "Well, you will desire to know what 

 has become of this man. His mind gave way; he became insane, and 

 he was sent to a lunatic asylum. In a biographical dictionary of his 

 country it is stated that he died there ; but this is incorrect. He re- 

 covered ; and, I believe, is at this moment a cultivator of vineyards in 

 Heilbronn. 



June 20th, 1862. 

 While preparing for publication my last course of lectures on 

 Heat, I wished to make myself acquainted with all that Mayer had 

 done in connection with this subject. I accordingly wrote to two gen- 

 tlemen who above all others seemed likely to give me tlie information 

 winch I needed. Both of them are Germans, and both particularly 

 distinguished in connection with the Dynamical Theory of Heat. Each 

 of them kindly furnished me with the list of Mayer's publications, and 

 one of them was so friendly as to order them from a bookseller, and to 

 send them to me. This fiiend, in his reply to my first letter regarding 

 Mayer, stated his belief that I should not find anything very important 

 in Mayer's writing^s ; but before forwarding the memoirs to me he read 

 them himself. His letter accompanying the first of these papers, con- 

 tains the following words : — " I must here retract the statement in my 

 last letter, that you would not find much matter of importance in 

 Mayer's writings: I am astonished at the multitude of beautiful and 

 correct thoughts which they contain ;" and he goes on to point out 

 various important subjects, in the treatment of which Mayer had an- 

 ticipated other eminent writers. My second friend, in whose own 

 publications the name of Mayer repeatedly occurs, and whose papers 

 containing these references were translated some years ago by myself, 

 was, on the 10th of last month, unacquainted with the thoughtful and 

 beautiful essay of Mayer's, entitled " Beitnige znr Dynamik des Him- 

 mels;" and in 1854, when Professor William Thomson developed in 

 so striking a manner the meteoric theory of the sun's heat, he was cer- 

 tainly not aware of the existence of that essay, though from a recent 

 article in * Macmillan's Magazine' I infer that he is now aware of it. 

 Mayer's physiological writings have been referred to by physiologists 

 —by Dr. Carpenter, for example— in terms of honourable recognition. 

 We have hitherto, indeed, obtained fragmentary glimpsecj of tiie man, 



