286 GREAT MEN OF SCIENCE 



in a well-known learned dictionary, which best shows the 

 complete indifference shown in Germany towards him 

 while still living. The report could not be rooted out; 

 Mayer had died in a lunatic asylum ! The fact that Tyn- 

 dall's championship of Mayer in London in 1862 finally 

 broke the spell, a final consideration of which may be left 

 to the calmer judgment of later times, has already been 

 mentioned. Age brought Mayer still a few quiet and com- 

 fortable years; three well-grown children survived him; he 

 died at the age of sixty-four.^ 



*As we stood around his grave,' says one of his biographers, 

 'a bitter feeling came over us. Suabia had given the world 

 two men of science of the first rank; Johannes Kepler died as 

 the result of want, while attempting to gain recognition of his 

 rights by the Reichstag in Regensburg. Robert Mayer was 

 misunderstood and insulted, until he was broken bodily and 

 mentally. A foreigner brought about a change in his treat- 

 ment at last. But he was now at rest; he had reached his 

 goal.* 



James Prescott Joule was an enthusiastic experimenter, 

 and a wide-ranging thinker with the highest point of view. 

 His most important work relates exclusively to the question 

 of the nature of heat, which at the time when he began his 

 work was still at the point reached by Rumford. In par- 

 ticular, the fact already recognised by Davy as of funda- 

 mental importance, the production of heat by the electric 

 current, attracted his attention from the start. He investi- 

 gated, and was the first to state the law of the production 

 of heat by electric current, known under his name to-day, 

 according to which the quantity of heat appearing in unit time 

 in a conductor is proportional to the resistance of the con- 

 ductor and the square of the current strength. 



^ E. Diihring, who had been banished from the University of Berlin, 

 later (1877) did his best by means of public lectures in Berlin to en- 

 lighten his contemporaries. See his Sache, Leben, imd Feinde, Leipzig. 



