386 CHAIN BRIDGE, 



by a link, at each place, suspended vertically, 

 and hanging within a strong pyramidal support 

 of cast iron with a quadrangular base. The 

 point of suspension is therefore moveable, by 

 the deviation of that link a little from the 

 perpendicular, and thus allows for expansion 

 and contraction in the cable. 



The side chains a b and e d, are nearly 

 inclined in equal angles to the horizon, and 

 the same may be said of the top links of the 

 catenary at b and D. 



3. To estimate the strength of the bridge. — 

 In an existing structure any of its dimensions 

 can be taken at pleasure, so as best to suit our 

 purpose 5 we shall therefore first assume as 

 known, the strength of the top link at b or d 

 of the catenary, its angle of inclination, and 

 that of the side chain, to the horizon; and 

 supposing a drove of oxen or any other weight 

 uniformly distributed over the bridge so as not to 

 alter the position of its parts, till it fails by the 

 fracture of the top link, we shall seek as follows. 



4. To find the horizontal tension, the weight 

 supported by the bridge, and the tensions of 

 the side chain and vertical link. 



