124 SECTIONAL ADDRESSES 
following, a trial of strength of the old system of building relatively to 
Mr. Dredge’s, with two models of bridges, each formed out of the same 
weight of iron wire, namely six ounces, was made in the Marquis’s garden, 
the Marquis and Lord Compton and others present. ‘The model upon the 
old system was first loaded. It bore 18 half-hundred weights, and with 
the next half broke down. The model formed upon Mr. Dredge’s principle 
sustained 34 half-hundreds when upon the addition of another half hundred, 
the wooden structure on which the chains were hung (answering to the 
towers of masonry, which form the fulcrum to suspension bridges) gave 
way altogether, and the bridge came down, but the chains were unbroken ; 
and upon Mr. Dredge’s calculation, would have sustained 500 more, making 
in all 2300 lbs. Mr. Dredge can build bridges on this plan, at one-third 
the expense of the present method : he requires only one-third the quantity 
of iron, and his bridge will be stronger and freer from vibration and 
pendulous motion. 
“TIT am, Sir, Your obedient Servant, 
“ WESTERN.” 
The long letter to the Rt. Hon. Viscount Melbourne from Lord Western 
contains many interesting passages : 
‘Having heard that Government is about to expend a further sum of 
money on the reparation of the Menai Bridge, which is said to be in a 
perilous state, I cannot refrain from entreating your attention to the vast 
improvement that has been made in the construction of suspension bridges 
by Mr. Dredge of Bath.... ‘He [Mr. Dredge] insists on the 
possibility of reconstructing the iron work of the Menai Bridge at a less 
sum than the superfluous iron would sell for, so much less is requisite than 
was there used ; and he pledges himself to the power of the bridge, if the 
irons are altogether altered and reconstructed on his principle, to be capable 
of supporting on transit 1000 tons. ‘The Menai bridge is believed to have 
cost near £150,000 and to have consumed in its construction about 2000 tons 
of iron and to be declared only capable of sustaining 733 tons on transit. 
Before submit .. . a detail ofsomeexperiments Mr. Dredge hasmade . 
I will endeavour to give some explanation . . . of the fundamental principle 
upon which his mighty fabric is erected. I must give it merely as it has 
struck my unlearned common sense, and which it has, from its simplicity, 
with a force so irresistible that it makes me believe I fully understand it.’ 
‘ I conceive the grand foundation may be said to be the rendering the chains 
strongest, and indeed very much the strongest, at the base, tapering them, 
by regular degrees to the centre, where they come at last, in fact, to a cipher. 
From the cipher commence, therefore, their size, weight and strength, 
which regularly increase, by degrees, quite up to its base, which base, you 
know, in a suspension bridge is the tower of masonry on which the chains 
are hung. In truth it is the application of that principle horizontally which 
is so obviously necessary in all perpendicular erections, of superior size 
and strength at the base, and tapering away to a cipher on its ultimate 
summit—as for example, the obelisk, the pyramid, the church spire ; and 
which principle he shows to be as effective horizontally applied as it is in 
the perpendicular, indeed, it may be said to be far more effective, as it has 
to support, in so difficult a position, comparatively with the perpendicular, 
its Own intrinsic weight and a heavy transit load besides. 
‘The main chains of the Menai bridge are the same size throughout, 
