ISO

A SINGLE ARCH

TRACT 5„

“ 5 . What additional weight will the bridge sustain ; andwhat will-be the effect of a given weight placed upon any ofthe before mentioned sections ?

“ 6 . Supposing the bridge executed in the best manner,what horizontal force will it require, when applied to anyparticular part, to overturn it, or press it out of the verticalplane ?

“ 7. Supposing the span of the arch to remain the same,and to spring ten feet lower, what additional strength wouldit give to the bridge.—Or, making the strength the same,what saving may be made in the materials.—-Or, if instead ofa circular arch, as in the plate and drawings, the bridge shouldhe made in the form of an elliptical arch, what would he thedifference in effect, as to strength, duration, convenience, andexpences ?

“ 8. Is it necessary or adviseable, to have a model madeof the proposed bridge, or any part of it, in cast iron. Ifso, what are the objects to which the experiments should hedirected ; to the equilibration only, or to the cohesion of theseveral parts, or to both united, as they will occur in the in-tended bridge?

9 . Of what size ought the model to be made, and whatrelative proportions will experiments, made on the model,bear to the bridge, when executed?

“ 10 . By what means may ships be best directed in themiddle stream, or prevented from driving to the side, andstriking the arch, and what would be the consequence ofsuch a stroke?

“ II. The weight and lateral pressure of the bridge beinggiven, can abutments be made in the proposed situation forLondon bridge, to resist that pressure?

“ 12. The weight and lateral pressure of the bridge beinggiven, can a centre or scaffolding be erected over the river,sufficient to carry the arch, without obstructing the vesselswhich at present navigate that part?

“ 13. Whether it would be most adviseable to make thebridge of cast and wrought iron combined, or of cast iron