JULIUS ROBERT MAYER was born at Heilbronn, November 25, 1814. He 

 received a medical education, and became first, county wound-physician and 

 afterwards city physician of Ileilbronn. But few particulars of his life have 

 been obtained. In 1840 he made a voyage on a Dutch freighter to Java, 

 and it was the accident of bleeding a feverish patient in this- country, and 

 observing that the venous blood in the tropics was of a much brighter red 

 than in colder latitudes, that led him to those investigations of natural 

 forces, the chief results of which are given in the following essays. Two 

 years after his attention was drawn to the subject in 1842, he published 

 his first paper on the " Forces of Inorganic Nature." It was put together 

 briefly, and published in Liebig's journal to secure the public recognition of 

 his claims. His second publication, " On Organic Motion and Nutrition " 

 (1845), an able essay of one hundred and twelve pages, is not yet translated. 

 His third paper, on "Celestial Dynamics," was published in 1848 ; and his 

 fourth, on the " Mechanical Equivalent of Heat," appeared in 1851. 



These vast and rapid labors were too much for his strength. His over- 

 tasked mind gave way, and he was taken to an insane asylum. He, how- 

 ever, fortunately recovered, and is now reported as occupied with the culti- 

 vation of the vine in Heilbronn. 



