1865.] in the Chains of Suspension Bridges. 143 



from 7'0 to 9'4 sectional inches, the power of the link to resist tension had 

 increased in about the like proportion, having rendered a force of nearly 

 240 tons necessary to produce fracture. 



Fig. 1 





Fig. G, 



Fig. 1. Link for Kieff Bridge. Depth of head 16 in., of centre 1O in., diameter of 



hole 4 in. 



Fig. 2. Elevation showing result of proof. 

 Fig. 3. Section through centre, showing result of proof. 

 Fig. 4. Experimental link, with wider head. Depth of head 18 in., diameter of hole 



4^ in. 

 Fig. 5. Link with properly proportioned hole for pin. Depth of head 17^ in., diameter 



of hole 6 in. 

 Fig. 6. Plan of chain, and section of pin and links. 



From subsequent experience, it has become evident that had the pins of 

 these chains been increased to 6j" diameters, giving a bearing surface of 

 10'2 square inches, the proper proportion between them and the body of 

 the links would have been very nearly arrived at, while with those of 

 only 6" diameter about an inch of the body of the links was wasted. 



The practical result arrived at by the many experiments made on this 

 very interesting subject is simply that, with a view to obtaining the full 

 efficiency of a li.ik, the area of its semicylindrical surface bearing on the 

 pin must be a little more than equal to the smallest transverse sectional 

 area of its body ; and as this cannot, for the reasons stated, be obtained by 

 increased thickness of the head, it can only be secured by giving a suffi- 

 cient diameter to the pins. 



That as the rule for arriving at the proper size of pin proportionate to 



