550 APPENDIX. 



much weakened through the inferiority of its 

 metal, as the bolts, similarly situated to it, at 

 the other three corners of the bridge, were all 

 when taken out a good deal bent. 



The joint A is of a description that may be 

 very commonly used, and the proper proportions 

 of its parts will differ according as the links 

 tend to hend the bolt or to shear it across. In 

 the former case the links and bars will not be in 

 contact, or will act on the bolt in a portion 

 only of their breadth, as at their centers ; and 

 if we reduce their thickness to that really acting 

 upon the bolt, the action of the joint would be 

 as in the figure below, where E and F represent 

 portions of the bars. 



K 



If then the distance of leverage in the bolt, 

 between the bars, be :=. twice that distance acting 

 at each end of the bolt to bend it, or AB = 2 BC, 

 the small link D sustaining the middle of the 

 bolt ought to be four times as strong as either 

 of the small links acting at the ends of it. 

 For, putting t for the tension exerted by one 

 of the small side links, during the fracture of 



