2 MECHANICAL FOUNDATION OF PHYSICAL SCIENCE. 



Joule each of them, made discoveries which alone rendered 

 generalization possible. And this was more particularly 

 the case with Joule's discovery of the law of conservation 

 of energy. This law, too, by completing the foundation of 

 physical science rendered possible the grand generalization 

 by which all branches of science are united in mechanical 

 philosophy ; so that it is to the memory of Joule that 

 mankind owes its gratitude for the grandest generalization 

 in the Universe — the complete mechanical foundation of 

 physical science. 



As a prelude to the biography of one whose work 

 constituted his life, to a degree far beyond what is usual 

 even with scientific men, it seems fitting to introduce his 

 own full and clear exposition of the objects and subjects of 

 his work, given after he had been led by his discoveries to 

 the full realizing of this general significance, but three years 

 before any philosopher was bold enough to follow him ; 

 and which as being the first exposition of the law of the 

 universal conservation of energy, has necessarily a place in 

 this Memoir. 



*" In our notion of matter two ideas are generally 

 included, namely, those of impenetrability and extension. By 

 the extension of matter we mean the space which it 

 occupies ; by its impenetrability we mean that two bodies 

 cannot exist at the same time in the same place. Impene- 

 trability and extension cannot with much propriety be 

 reckoned among the properties of matter, but deserve 

 rather to be called its definitions, because nothing that does 



* "On Matter, Living Force and Heat." By J. P. Joule, Secretary of the 

 Manchester Literary and Philosophical Society. A Lecture at St. Ann's 

 Church Reading- Room. 1847. 



