vii LAW AND PRINCIPLE 181 



of the British Association before whom the experiments 

 were described in 1843, Joule being then a young man 

 of twenty-five years of age, completely unknown in 

 the scientific world. Genius dwells with the Gods 

 on Mount Olympus, and only a few daring spirits climb 

 up from the valleys to worship at its shrine. This is 

 as true of science as it is of art, or literature, or music. 

 Commonplace work can be understood by the many, 

 but original conceptions demand effort to comprehend 

 them, and they are, therefore, usually unregarded, or 

 if noticed, condemned. 



Undaunted by the chilling reception which his com- 

 munication received, Joule continued his researches, 

 and in 1845, and also in 1847, he presented accounts of 

 further investigations to two other meetings of the 

 British Association. On the latter occasion he was 

 asked by the chairman of the section to confine himself 

 to a short verbal description of his experiments ; and 

 his work would again have gone unheeded but for the 

 presence of another young man, William Thomson, 

 afterwards Lord Kelvin. What happened was described 

 many years afterwards by Joule himself : 



Discussion not being invited, the communication would have 

 passed without comment if a young man had not risen in the 

 section, and by his intelligent observations created a lively 

 interest in the new theory. The young man was William 

 Thomson, who had two years previously passed the University 

 of Cambridge with the highest honours, and is now probably 

 the foremost scientific authority of the age. 



Joule's discovery of the mechanical equivalent of 

 heat was not a result stumbled upon accidentally, but 

 a consequence of rigorous experiment, precise measure- 

 ment and philosophic thought. After he had assured 

 himself of the truth of the principle, Joule devoted 



