APPENI^IX. 551 



the bolt, 2 / would be the tension in D required to 

 break the bolt in the middle, if it were not 

 sustained at its ends by the small side links; 

 and therefore 4 t would be required to break 

 it in the middle, when it is sustained by them; 

 since a beam firmly fixed at the ends will bear 

 twice as much as one merely supported there. 

 If the joint contain a greater number of bars 

 than two, it is evident that all the internal small 

 links must be equal in strength, and each four 

 times as strong as one of the side links. As 

 to the absolute strength of the small links, that 

 ought to be regulated so that the sum of their 

 sections shall be equal to the sections of the 

 bars ; and the thickness of the bolt must be 

 such as to prevent the tension t, of either of 

 the small side links, breaking the bolt across 

 with its leverage. 



If the tendency of the chain is to shear the 

 bolt across, and not to act by leverage, the 

 links and bars in the joint A must be in contact 

 and act on the bolt through their whole breadth. 

 The small link sustaining the middle of the 

 bolt ought then to possess double the strength 

 of either of the small side links ; for it would 

 have to shear the bolt through in two places, 

 and a side link would have to cut it only in 

 one. — ^This disposition of the joint is better 



