

CHAPTER XIII. 



EXPANSIBILITY DIFFERENT FROM IMMOBILITY, 



AND MOBILITY, FROM FLEXIBILITY AND 



ELASTICITY. 





So totally and absolutely inert is the solid 

 matter of which the world is composed, that it 

 possesses, within itself, no power by which it 

 can act; neither the mass altogether, more than 

 the smallest particle of sand, would ever alter in 

 form or in position, unless it were acted upon 

 by agents external to itself. It is in conse- 

 quence of this natural tendency in solid matter 

 to remain permanently the same, offering resist- 

 ance alone to the action of those bodies by 

 which it may be assailed ; that it is said, to be 

 imbecil and inert, and to which, the term immo- 

 bility ought especially to be applied. 



Whenever solid matter is acted upon, and 

 the resistance which it opposes is overcome ; 

 the changes which it is made to undergo per- 

 petually wear away : it gradually verges from 



