9 AUGUST 1856, Page 13

TIlE BRIDGES OF LONDON.

How is it, asks every one who is acquainted with the state of the Westminster Bridge affair, that the practical judgment and skill of Rendell and Simpson are called in to report upon the efficiency of the construction, after the works have advanced so far? Why is it that their experience was not consulted at an earlier stage—say, upon the working drawings, before at least the design was accepted, or before the work was commenced ? The question may be answered from the whole history of the London Bridges. Situated on one of the finest navigable rivers in the world, unsurpassed in the magnitude of its population or its traffic, London has nevertheless, in proportion to its extent of population, fewer communications between its two shores than any city in the world. For many centuries but one bridge spanned the river. The second bridge, Westminster, was opened in 1750; the third, Blackfriars, in 1766—it was then a toll-bridge. Yet three bridges for the London of 1766 gave a larger proportion than the six bridges of the present day, particultirly when we take into account the indifferent means of transit between these six bridges. Nearly half a century elapsed before Rennie brought forward proposals for two others—Southwark, opened in 1815; Waterloo, in 1817; with new London Bridge. Rennie lived to see the first and second designs completed, not the third. One month after Waterloo Bridge was opened, Vauxhall was finished, after the designs of James Walker —a very useful addition to the transit of the river, although at ihat day even more than at present lying wide from the centre of the metropolitan traffic. Its use indeed, was then chiefly extra-metropolitan. When it was resolved, after the death of Rennie, to build a new London Bridge, the Corporation very judiciously looked into his portfolio, and took from it the design of that structure which is the best monument of his bold and skilful engineering.

In all cases, however, it has happened that the work has been handed over in the lump to the absolute disposal of some individual; and perhaps the success of the earlier engineers assisted a modern tendency in establishing a custom of throwing these great works into the hands of individuals. We have seen a recent instance in the palace-building at Westminster, which has not been so fortunate in its results. The subsequent history of . two of the bridges show i the effect of this plan of blindly accepting individual workmen. Blackfriars Bridge became sickly : ' the structure had lasted for some time ; the bed of the river was not the most stable ; and the engineer who was employed suggested. a plan of under-pinning as a mode of strengthening its foundations throughout. The plan was accepted, and for some years the Corporation expended nearly 19,000/. a year on the works. The plan was promising, but it was damaged by one curious 'recess at the last. In order to get at the founda tions coffer s were constructed : they form a solid wall round the Part upon which the builders have to operate, and the water being withdrawn, the place is open to the workmen. These cofferdams were constructed by .driving in piles close together. The works were completed, the cofferdams were no longer necessary, and they had of course to be removed. But there were two modes of removing them : the mode chosen was to draw out the piles, with the result of so unsettling the soil that a dangerous • subsidence of the bridge occurred. It required a very little sagacity to perceive that the better mode would have been to cut off the piles at the surface of the bed of the river. Notwithstanding this experience the same person was called in to doctor Westminster Bridge. The history of this edifice is curious. It was originally built by Labylle, and was constructed with stone piers, solely to carry a wooden superstructure for foot, passengers. After the cominencement, however, the architect 'was required to convert, it. into a carriage-bridge. He enlarged • his caisson, and sank piers sufficient to support the substantial • carriage-way, which lasted for many. years. The stability of the enlarged bridge depended greatly upon the ingenious arrangement of the massive masonry of its superstructure ; but when at last the bridge began to give way under the effects of time and an enormous traffic which' the architect never contemplated, the process to which it was subjected was exactly that which should –have been most avoided. The superstructure was removed as too "heavy," apparently in ignorance that its construction assisted -'the stability of the bridge. Nearly half of the navigation of the river has been encroached upon by a wooden substructure—a trap for the toiling lighterman, and a disfigurement in the sight of every foreign visitor. Surely the Stephensons or the Rennies might have been called in to decide upon plans before committing the purse if not the person of the public to doubtful makeshifts. But how is it with the most important of these public works ? . The new bridge at Westminster has crept. into partial existence without public inquiry or first-rate _scientific consideration. We , hear the plan denounced as an expensive novelty, with glaring defects of construction, rendering its stability and even its public • utility doubtful. It is questioned,. from the construction of the bridge, whether its several parts will consent to a uniform " settlement " ; whether its stilted foundations will stand the wear • and tear of many years ; whether its diminished headway, as compared with the bridges., above and below may not inflict in' convenience if not danger on the craft that hits to pass ; whether the obtrusion of its ribs or girders above the roadway, dividing its traffio into coming and going, may not impede the passage, and even endanger property and life by the obstruction. How is it that these things can happen ? We have already pointed out the reason. The fact that the precedents have in some instances happened to succeed, strengthened by a growing tendency, has induced those who are officially responsible to place tasks of this kind—we will . not call them " jobs "—into the hands of individuals. The Houses of Parliament are the great feature in the district, and perhaps there was some notion of making the bridge harmonize with them, not only in its outward aspect when finished, but in the morale of its contract management. After the scheme is commenced, competent persons have been appointed to investigate, and they report accordingly. "The present scheme," they say, is devised with a view to the avoidance of the use of coferdams or caissons for founding the piers and abutments. This is done by forcing the piers below low-water by a series of wooden piles, surrounded by a sheeting of east iron; the space enclosed by this sheeting being filled in with concrete." But they do not state that this shield. ing is formed by long pannels of cast-iron about three feet wide, which slip into -grooves of little depth ; wherefore the greatest accuracy is essential to fit them between the cast-iron face piles which are grooved on both sides to. receive them ; so that any

• violent strain might unsettle them. "With a view to prevent the cast-iron piles being laid bare by the scour of the river beyond a fixed limit, namely three feet below low-water, it is proposed to surround them up to that height with a bank of concrete ; and in order to guard the piers . masonry, as well as cast-iron piling, from accident by the fouling of barges, steamers, or otherwise, they are to be protected by fleeting booms." These floating booms ought to have raised evenan, the official mind some suspicion as to the stability and sufficiency of the design. The bridge is an example a converse to corroborate the one main

• point in Sir Charles Trevelyau's large plan of improvement for the same neighbourhood : the general .design ought to have been , open to public competition, and the works of the artists should

• have been submitted to the public after the selection, with ample 7 opportunity for the intervention of Parliament. There could have been a second competition for the working designs ; with. premiums, perhaps, sufficient to remunerate the competitors, but with e. perfectly open choice for the responsible Government in

the selection of the design, and. afterwards of the men to carry it out.