Professor TyndaVs Lectiire oji Force. 2-51 



in the tropics was of a much brighter red than in colder latitudes, 

 and his reasoning on this fact led him into the laboratory of natu- 

 ral forces, -where he has worked with such signal ability and suc- 

 cess. 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 recovered ; 

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

 Heilbronn. 



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 gentlemen who above all others seemed likely to 

 give me the information which 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 friend, in his reply to my first letter regarding Mayer, 

 stated his belief that I should not find anything very important 

 in Mayer's writings; but before forwarding the memoirs to me 

 he read them himself. His letter accompanying the first of these 

 papers, contains 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 wiitings : I am astonished at the mul- 

 titude 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 anticipated 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 *' Beitrage zur Dynaraik des Himmels ;" and 

 in 1854, when Professor William Thomson developed in so 

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

 certainly not aware of the existence of that essay, though from a 

 recent number in Mo.cmillan^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 glimpses of the man, partly from physicists and partly 



