382 FRAGMENTS OF SCIENCE. 



June 20, 1 862. 



While preparing fur publication my last course of 

 lectures on Heat, I wished to make myself acquainted 

 with all that Dr. Mayer had done in connection with this 

 subject. I accordingly wrote to two gentlemen who 

 above all others seemed likely to give me the informa- 

 tion which I needed. 1 Both of them are G-ermanp, and 

 both particularly distinguished in connection with the 

 Dynamical Theory of Heat. Each of them kindly fur- 

 nished me with the list of Mayer's publications, and one 

 of them [Clausius] 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 impor- 

 tant in Mayer's writings; but before 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 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 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 'Beitrage zur 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 certainly not aware of the 

 existence of that essay, though from a recent article in 



1 Helmholtz and Clausius. 



