CHAPTER VII. 



THE Year 1847. — Lecture at St. Ann's Church Reading 

 Room. — Conservation of " Force!' — Fresh Determination 

 of Equivalent. — Verification of Laplace's TJieory of Sound. 

 — foule's Paper accepted by the Institute of France. — 

 Meeting of Britisli Association at Oxford. — First Public 

 Recognition of foule's Discoveries. — foule's Account. — 

 Sir William Thomson's Account. — Marriage. — Shooting 

 Stars. — The Adoption of Herapath's Hypothesis. — Deter- 

 mination of Velocities of Molecules of Gases and Theoretical 

 Specific Heats. 



1847 proved a most important year in the life of Joule, 

 although at its commencement, whatever reason he may 

 have had to expect that it was to be the year of his 

 marriage, he had no reason to foresee the fortunate influence 

 on his scientific career which the events of this year were to 

 exercise. By the end of 1846 he had completed nearly all 

 the investigations he had been engaged upon. He had 

 made himself master of the significance of the principle 

 we now call energy in all its physical and mechanical 

 modes, and he had received his first scientific honour — the 

 highest this society could then award him — in his election 

 to the office of secretary. Thus, whatever it might prove 

 in his family relations, 1847 must have opened to him as 

 likely to be a quiet year in his scientific work. 



On the 28th April, 1847, Joule gave a popular lecture in 



