250 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[Jury, 



however, directly at variance with Mr. Barry's. In " Pratt's Mathe- 

 matical Principles of Mechanical Philosophy," — considered a standard 

 work, and, as we are informed, a text-book at Cambridge, — the theory 

 is so clearly explained, that we give it in his own words : " A pointed 

 arch," he says, " must have a great pressure on its crown to prevent 

 its falling, because it may be considered as consisting of two extreme 

 portions of a very large circular arch brought together, so that the 

 pressure on the crown must at least equal the pressure of the portion 

 of the circular arch which is removed. Flving buttresses alwavs have 

 a great pressure upon their highest part. The pointed arch will sus- 

 tain almost any weight on its crown, provided the lowest stones do 

 not give wav, and, consequently, the Gothic arch is stronger for lofty 

 '"Hidings than the circular ; but the circular arch is far better adapted 

 •nan the (iothic arch for bridges, since the pressure of weights pass- 

 ing over may act upon any part of the arch, not onlv on the crown." 

 Mr. W newel I comes, in different words, to the same conclusion ; and 

 The same can be deduced from Attwood, though not so clearly express- 

 ed. These are no mean authorities ; indeed, we do not know an ex- 

 ception in any author, British or foreign, to the opinion, that the 

 pointed arch requires a greater thickness of material at the crown 

 than the circular arch to keep it from rising ; and if so, the sub- 

 stitution of the pointed arch should, in place of allowing a reduction, 

 demand an addition to the least thickness required for the present 

 arches. Add to theory, the experience of every modern engineer of 

 this or other countries, as shown in their bridges of any considerable 

 size : for we are not aware of any example of a pointed arch for a 

 bridge of any magnitude in the works of Smeaton, Rennie, Telford, 

 Perronet, or indeed of any other. 



Mr. Barry's second argument for substituting the pointed arch is — 

 " the elevation ot its springing above the level of high water, by which 

 the water-way of the bridge will be the same at all times of the tide, 

 in place of being contracted by the present spandrils at high water, 

 nearly equal to one-twentieth of its sectional area, occasioning eur- 

 'ents, with a fall, and sometimes danger to craft in passing through 

 ihe bridge under the influence of high winds." Mr. Barry appears 

 aere to have stated "sectional area," when he must have meant width 

 or chord ; for we rind, that in the section of his scheme, the contrac- 

 tion of the middle arch by the spandrils is about one-twentieth of the 

 width, at the level of Trinity high water ; but as the contraction is 

 only a few feet in depth, before the arch falls into the vertical line of 

 ihe pier, the diminution of sectional area i9 not one-twentieth, nor 

 more than one one-hundred-and-twentieth, and this at high water onlv: 

 — and even this small diminution is in effect reduced practically to 

 notning as respects the current, when it is considered, that the great- 

 est velocity does not take place until half ebb, bv which time the water 

 has sunk below the level of the spandril. It is, we think, therefore 

 evident, that the proposed alteration will not produce anv useful effect 

 jpon the currents or the falls. When the bed of the river under the 

 arches is lowered (which also is part of the contract), and the coffre- 

 uams removed, the present current through the bridge will be materi- 

 ally lessened. Some practical good would be effected bv the higher 

 point of springing of the pointed arches, in giving more head room 

 lor craft near to the piers ; and, as the Westminster-bridge arches 

 have less space for navigation than anv of the four City bridges, anv 

 .ncrease of accommodation is desirable ; unfortunately, however, 

 while an addition is thus made for one-fourth of the width of the arch 

 near the springing, a portion is taken away from the height for the 

 remaining three-fourths, nearest the crown,"where it is of the greatest 

 importance ; this diminution varies from eighteen inches to thirty 

 inches ; so that the centre arch will not then have more height for 

 navigation than the two arches, adjoining the centre arch now have ; 

 and when we inform you, that at high water of good tides, the centre 

 arch is the only one which some of the steamers can conveniently pass 

 inder, we think you will allow with us, that the proposed lowering 

 will, in such cases, be rather a practical evil, as it will take from the 

 convenience of what is now the least convenient bridge for navigation, 

 :o say nothing of the liability to the ribs being iojured by masts and 

 chimneys striking them. 



The artistic point of view is the last insisted on by Mr. Barry j and 

 on this, what we may say, is with a due respect to his better judgment 

 and taste in matters of architecture. The contract with Mr. Cubitt 

 does not alter the present elevation below the crown of Ihe arches ; 

 but, as you are aware, we have long since suggested that a new ele- 

 vation for the bridge after the Norman style would he a great improve- 

 ment. In this, however, we would not propose to reduce the magni- 

 tude of the features of the bridge, considering that simple boldness, 

 and strength, are essential qualities in a bridge over the river Thames, 

 in London ; aud if so, that it is scarcely fair to reduce the parts of the 

 bridge because those of the elegant florid edifice, which is now being 

 erected near it, are small. For palace architecture, the latter may be 



the best, and we do not venture an opinion as to the effect of Mr. 

 Barry's work, in which our professional employment was confined to 

 the construction of the colfre-dam and the river wall ; but for a bridge, 

 particularly in a city, with constant and heavy rough trade under and 

 over it, the style of architecture ought, we conceive, to be more mas- 

 culine. Mav not the new houses be better displayed thus, than by 

 accordance of style ? The beauty of the detail of the new houses is 

 verv great : the length SOU feet, without, at present, anv striking fea- 

 ture or variety, also great ; but we submit, whether an additional 800 

 feet of according composition and style, of still lower elevation, 

 would not rather tend to render the " ensemble" dull and flat than 

 effective ? The style of the new buildings must stop somewhere. 

 < an it do so better than at the bridge, which, as we have already said, 

 appears to require a character different from the Houses of Parliament ? 

 If both faces of the arches are proposed by Mr. Barry to be alike, 

 would there not be a want of accordance between the north face of the 

 bridge and the buildings and mansions near to it, and which there is, 

 we presume, no intention of altering ? Is a continuance of the same 

 stvle required for so great a length, as the houses and the bridge to- 

 gether, although the pointed may be the prevailing character of the 

 building ? Does not precedent reply to this in the negative, and 

 prove it, by the fact that the periods of the original erection and of 

 the additions that have from time to time been made to some of our 

 finest buildings may be discovered by the style ; the Saxon, the Nor- 

 man, the Pointed, and varieties of each being found iu the same build- 

 ing, and vet the " ensemble" not inharmonious. We hope, therefore, 

 that the superstructure of the bridge, thuugh it may be different in 

 stvl p from the Houses uf Parliament, may not be discordant, 



Westminster-bridge has been where it is, and as it is, for a century t 

 it was th°re when the designs for the new houses were made, aud we 

 never heard that to pulldown Westminster-bridge touearly low water, 

 was to be a necessary accompaniment to the adoptiou of any of the 

 designs. If you and the other commissioners had known that such 

 alterations were contemplated, you would not, we are sure, have 

 allowed the works to have proceeded as they have done, until nearly 

 two-thirds of the whole to above high water had been completed, in- 

 cluding the renewal or repair of the arch stones. 



We may name here an objection to the form which Mr. Barry has 

 proposed for the arches, as tending to lessen the stability of the bridge. 

 l.ahelve considered that by adopting the seuii-ciie.ular arch, which 

 presses vertically upon its piers, each pier might be considered an 

 Abutment, so that if one arch were to give way, the piers would sup- 

 port all the others. From the great height at which the proposed 

 pointed arches spring from the piers, and their greater lateral pres- 

 sure or thrust upon the piers, the above would not be the case. On 

 the contrary, the failure of one arch would, we conceive, cause the 

 destruction of all the piers and arches. This consideration is not to 

 be disregarded in a bridge, the piers of which have been so badly 

 Founded, that to support t.iem has been a constant expense, and is at 

 this moment a source of considerable anxiety ; although the works we 

 have in hand, if as successful as hitherto, will render the piers much 

 more secure than they have ever been ; we hope, perfectly so. 



(in the whole, therefore, we have reason to be pleased, that Mr. 

 Barrv approves the various improvements in the bridge which the 

 commissioners have contemplated) and, with one exception, contracted 

 for. The only addition he makes to them is, the substitution of the 

 pointed arch, which, for the reasons stated, we cannot advise. We 

 agree to the advantage, in point of taste and utility, of keeping the 

 road-way of the bridge low; we have designed doing this as far as 

 can be done, having regard to the funds of the commissioners, and 

 therefore without disturbing the present arches. There is a way oy 

 which the height of the road-way might be reduced below what either 

 Mr. Barrv or we have yet proposed, at one-fourth of the expense ot 

 his plan (which would, we think, much exceed his estimate), and 

 without lowering the soffit of the arch, or diminishing in any way the 

 convenience of navigation; but we avoid entering upon, or committing 

 ourselves to this, until we have considered the subject more iu detail, 

 ami understand it to be the wish of the commissioners that we should 

 do so; for the works we have already recommended may go as far ac 

 their unassisted funds would justify. 



We. have the honour to be, 

 Sir, 

 Your obedient servants, 



23, Great George Stntt, Walker and Burges. 



3lslMay, 184a 

 The Rt. Hon. Charles S. Lefevrk, 

 Speaker of the House of Commons, 



Chairman of the Commissioners of Westminster Bridge. 



