FLEXIBILITY AND ELASTICITY. 259 



possessing any inherent power of unbending 

 themselves, is therefore called flexibility ; or as 

 Dr. JOHNSON expresses it, " the quality of 

 admitting to be bent." The nature of this 

 capacity to be acted upon, is exemplified in a 

 common piece of iron or of wood. The parti- 

 cles of matter, of which these substances are 

 composed, are unable to resist the power which 

 acts upon them. The inferior strata become 

 contracted, the upper lengthened, both are dis- 

 torted and bent; and finally, if the external force 

 be increased beyond a certain point, the bond 

 of continuity between* the individual particles 

 becomes separated, and the iron or wood snaps 

 or breaks. The whole effect which has been 

 thus produced, is evidently to be referred, not 

 to a power resident in these bodies, but to the 

 agency of the external force impressed upon 

 them ; it was resistance overcome by an over- 

 coming force. 



This capacity of admitting to be bent and to 

 be moved by an external force, which flexible 

 bodies possess, extends to other bodies which 

 have the power of restoring themselves to their 

 former situation, after the external force is 

 removed, through the agency of which they 

 had been made flexible : bodies such as these, 

 are called elastic; of this description are steel, 

 whalebone, catgut, &c. &c. The distinction, 

 therefore, which exists between elasticity and 



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