290 FRAGMENTS OF SCIENCE. 
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 
