290 FRAGMENTS OF SC1KNCE. 



even to scientific men his merits are but partially known. 

 Led by his own beautiful researches, and quite independ- 

 ent of Mayer, Mr. Joule published in 1843 his first paper 

 on the " Mechanical Value of Heat;" but in 1842 Mayer 

 had actually calculated the mechanical equivalent of heat 

 from data which only a man of the rarest penetration could 

 turn to account. In 1845 he published his memoir on 

 " Organic Motion," and applied the mechanical theory of 

 heat in the most fearless and precise manner to vital 

 processes. He also embraced the other natural agents in 

 his chain of conservation. In 1853 Mr. Waterston pro- 

 posed, independently, the meteoric theory of the sun's heat. 

 and in 1854 Professor William Thomson applied his 

 admirable mathematical powers to the development of the 

 theory; but six years previously the subject had been 

 handled in a masterly manner by Mayer, and all that I 

 have said about it has been derived from him. When we 

 consider the circumstances of Mayer's life, and the period 

 at which he wrote, we cannot fail to be struck with 

 astonishment at what he has accomplished. Here was a 

 man of genius working in silence, animated solely by a love 

 of his subject, and arriving at the most important results 

 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 brighter red than in colder latitudes, 

 and his reasoning on this fact led him 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, it is alleged, gave 

 way; it is said he became insane, and he was certainly 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. 



June 20, 1862. 



While preparing for 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 



