JOURNAL 



OF THE 



ASIATIC SOCIETY. 



JANUARY, 1848. 



Memoir upon the Quantity of Iron necessary in a Tension Chain 

 Bridge. — By Rev. J. H. Pratt. 



To demonstrate, that the quantity of iron in a Suspension 

 Bridge, necessary to enable each part to sustain the greatest tension 

 to which it will be subjected when the road-way is loaded to the 

 greatest extent, is altogether independent of the form of the 

 bridge, however complicated that form may be, and depends 

 solely upon the width of the bridge, the height of the piers above the 

 road-way, the thickness of the first link in leaving each pier, and the 

 angle that link makes with the horizon. 



In the controversy recently mooted in India regarding the superiori- 

 ty or inferiority of Taper-Chains in the construction of Suspension 

 Bridges, when compared with uniform or common-chains, the consi- 

 deration of the Quantity of Metal employed is one of considerable prac- 

 tical importance. According to the remarkable property which we 

 have above enunciated, and shall soon proceed to demonstrate, the 

 Quantity of Iron actually necessary to resist the strains is in theory 

 the same for all forms and positions of chain and suspending rods. But 

 this property points out to us, that in the actual construction of 

 Bridges the quantity of metal employed will be greater in proportion to 

 the greater variety of strain. For there would always be a practical 



No. XIII.— New Series. b 



