ON 



seemed likely to give me the information which I 

 needed.* Both of them are Germans, and both particu- 

 larly 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 [Clansius] 

 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 be- 

 fore forwarding the memoirs to me he read them himself. 

 His letter accompanying them 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 

 writings: I arn 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 anticipated other eminent writers. 

 My other 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 " Bei- 

 trage zur Dynamik des Himmels/' and in 1854, when Pro- 

 fessor \Villiam 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 

 article in " Macmillan's Magazine " I infer that he is now 

 aware of it. Mayer's physiological writings have been re- 

 ferred to by physiologists by Dr. Carpenter, for example 

 in terms of honoring recognition. We have hitherto, in- 

 deed, obtained fragmentary glimpses of the man partly from 

 physicists and partly from physiologists; but his total merit 

 has never yet been recognized as it assuredly would have 

 been had he chosen a happier mode of publication. I do 

 not think a greater disservice could be done to a man of 

 science, than to overstate his claims: such overstatement is 

 sure to recoil to the disadvantage of him in whose interest 

 it is made. But when Mayer's opportunities, achievements, 

 and fate are taken into account, I do not think that I shall 

 be deeply blamed for attempting to place him in that 

 honorable position, which I believe to be his due. 



* Heliiiholtz and Clausius. 



