260 FLEXIBILITY AND ELASTICITY. 



flexibility consists in this ; elasticity has the 

 capacity to be bent, and the power to restore 

 itself to its natural and original situation from 

 whence it had been forcibly distorted and with- 

 held ; while flexibility, on the contrary, has the 

 capacity to be bent only, without the power of 

 unbending itself. Dr. JOHNSON, therefore, with 

 that wonderful power of discrimination which 

 on every occasion he is found to possess ; very 

 properly defines elasticity, to consist of a " force 

 in bodies by which they endeavour to restore 

 themselves to the position from whence they 

 were displaced by an external force." By the 

 substraction of which, such is the peculiarity 

 in the arrangement of which the elastic sub- 

 stance is composed, that it has the power of 

 returning back to the position it was in before, 

 in which condition it remains. 



That the return to its original situation only 

 of the elastic body, by the snbstraction of the 

 external force; is the true meaning and applica- 

 tion of the w r ord elasticity, is further proved by 

 Sir ISAAC NEWTON. In his book on optics, he 

 says, " when a body is compact, and bends or 

 yields inward to pressure, without any sliding of 

 its parts, it is hard and elastic, returning to its 

 figure with a force arising from the united at- 

 traction of its parts." If we, therefore, exa- 

 mine the definition of the word elasticity as 

 {riven- by Johnson, and illustrated by Newton, 



