430 Mr. Seaward on Suspension Chain Bridges. 



Table of the Length, Sectional Area, 8)-c., of the diagoiial Rods. 



No. 



] 



2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 



rod 

 do. 

 do. 

 do. 

 do. 

 do. 

 do. 

 do. 

 do. 

 do. 



bV>, 

 cB, 

 dB, 

 eB, 

 /B, 

 ^B, 

 //B, 

 ^B, 

 AB, 



Length of Rod. 



Feet. 



193-46 



175-13 



156-82 



138-61 



120-55 



102-75 



85-27 



68-48 



52-87 



40-03 



Strain. 

 Tons. 

 87-93 

 79-12 

 71-28 

 63-00 

 54-79 

 46-70 

 38-75 

 31-13 

 24-03 

 18-19 



Sectional Area 

 in square inches, 

 allowing 7 tons 

 per square inch. 



Inches. 

 12-56 

 11-30 

 10-18 



9- 



7-82 



6-67 



5-53 



4-45 



3-43 



•2-60 



Cubic inches 

 of metal in 

 each rod. 



Inches. 



29-158 



23-747 



19-157 



14-969 



11-312 



8-224 



5-658 



3-656 



2-176 



1-249 



119-306 

 And for the two ends of the bridge 2 



238-612 



28-8 tons 

 9-6 



1-1 



Equal to 

 Add one-third extra tor joints 



(N. B. From there being no necessity of having the 

 rods in short pieces, as is the case with the chains, one- 

 third extra woukl not be requii-ed for the joints ; but as 

 there will be something additional for bolting the rods 

 to the platform, the same allowance is made here.) 



Add for struts Ic, le, li, &c. for keeping ) 



the rods straight J 



Total . 39i tons 

 Making a total of 39^ tons of metal in the rods, being the 

 same quantity as would be required for the chain.s, as already 

 shown ; but with this impoi'tant difference, that while the strain 

 upon the catenary curve would be equal to 1 5 tons per square 

 inch of sectional area, upon the diagonal rods the strain 

 would be only 7 tons per square inch. Whence it is mani- 

 fest that, by adopting the new plan, a suspension bridge might 

 be built with the same quantity of materials, and possessing 

 more than double the sti'ength of one built on the old plan of 

 the catenary curve. 



It is right here to observe, that the plan is not entirely fi-ee 

 from objections: several have been made; but the only one 

 which appears to be deserving of particular consideration is 

 tlie following, viz. " Supposing it to be perfectly true that, by 

 employing the diagonal rods in a suspension bridge, the strain 



