440 THE STRENGTH 



merit proportionnel k leur distance du milieu 

 de la piece, et par consequent que le mime 

 poids qui agit sur une Jibre, parallUement ct 

 sa longueur^ soit pour la tirer, soit pour la 

 rejouler, Valonge on la raccourcit de la meme 

 quantitL Ici les fibres avaient perdu leur force 

 elastique; la propriete qu^elles ont presentee 

 existe done, a plus forte raison, lorsque Taction 

 qu'elles ont eprouvee n'a pas detruit cette 

 elasticite. 



29. The intention of the preceding experi- 

 ments, on the elasticities of cast and wrought 

 iron, being to prepare in some degree the way 

 to an inquiry into the best form of beams of 

 those metals, particularly of cast iron, we will 

 now reconsider the strain, which beams are 

 subjected to, with a view to their proper 

 formation to obtain the utmost strength. If, 

 then, we conceive a beam, supported at its 

 ends, and bent by a weight any where laid upon 

 it, we have seen that all the bottom fibres or 

 parts must be in a state of tension, and the top 

 ones in a compressed state, and if C and D 

 be the centers of tension and compression, the 

 forces in C will be just equal to those in D, 

 where D may be considered as the fulcrum of 

 the bent lever DCA. 



