282 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



[AvauST, 



upon which an opposite conclusion is founded in Messrs. Walker and Burges' 

 report is erroneous." Both theory and practice confiim me in the opiniou 

 which I have advanced in my report, that a pointed arch requires less thick- 

 ness at the crown than is usually considered necessary for a circular arch. 

 As, however, it might possibly be inferred from the observations of Messrs. 

 Walker and Burges that the arch which I have proposed is not strong enough 

 for its purpose, although they do not attempt to prove that such is the case, 

 I have thought it right to enter into a careful investigation of its properties ; 

 from which I am fully convinced, that I have not carried the principle which 

 I have advocated far enough ; and that, considering the insignificant span 

 of even the largest of the proposed arches, it would be no great effort of 

 engineering science to reduce the thickness of its crown to nearly one-half 

 of what is proposed by Messrs. Walker and Burges; by which meaus the 

 lowering of the road-way over the centre arch might be carried to the extent 

 of 6 feet 6 inches, instead of 3 feet G inches, even without reducing the 

 clear height of the centre arch as I have proposed ; if such reduction were 

 deemed to be an objection of any importance. In this opinion I am con- 

 firmed by the examples of numerous stone bridges both in this and other 

 countries, and also by the judgment of several eminent engineers and mathe- 

 maticians of the present day. 



With reference to the loss of water-way, which 1 stated was occasioned by 

 the haunches or spandrils of the present arches at high water, 1 ought per- 

 haps to have explained that I referred to such portion only of the water-way 

 as is affected by those obstructions, which might, however, I think, have 

 been inferred: With regard to the removal of these obstructions, I do not 

 agree with Messrs. Walker and Burges in thinking that it would be unproduc- 

 tive of any useful effect upon the " currents and falls ;" and I consider the 

 arguments in support of their opinion to be fallacious, inasmuch as they are 

 founded upon the assumed level of high water according to Trinity standard ; 

 whereas the present ordinary spring tides, as the] must be well aware, rise 

 considerably above that level ; on one extraordinary occasion recently as 

 much as 3 feet inches. That some practical good would be effected in 

 giving more head room for craft near to the piers, by raising the springings 

 of the arches according to my suggestion, Messrs. Walker and Burges admit ; 

 and I conceive that this advantage alone ought to be a sufficient inducement 

 to remove the present arches and to substitute others of more convenient 

 firm ; but when it is considered that the opportunity would be thereby af- 

 forded of lowering the road-way to nearly double the extent proposed by 

 Messrs. Walker and Burges, without producing the slighest injury to the na- 

 vigation of the river, the advantage as regards the convenience of the public 

 is so much enhanced, that the propriety of rebuilding the superstructure 

 cannot, T think, be doubted, With respect to m\ proposition of lowering 

 the centre arch 18 inches, which it appears Messrs. Walker am] P.urges con- 

 sider will be " rather a practical evil,'' as affecting the navigation of the 

 river, it is necessary that I should call your attention to the clear height of 

 the middle openings of some of the bridges above Westminster Bridge, as 

 they have done to those only which are below the bridge. While the clear 

 height of the centre arch of Westminster Bridge is 26 feet above Trinity 

 standard of high water, the centre openings of the modern bridges at Vaiis- 

 hall and Hammersmith are of the respective heights of 25 feet 4 inches, 

 and 10 feet 1 inch, to say nothing of those of llattersea and Putney Bridges, 

 which are much less, but which I admit are extremely inconvenient. As the 

 largest steamers which pass up the river are f bos. which ply between London 

 Bridge and Richmond, and as their funnels arc jointed so as to allow of 

 their of passing even under Putney Bridge, the height of the centre opening 

 of which is only 11 feet 2 inches above high water, it cannot be imagined 

 that the lowering of the centre arch of Westminster Bridge to the extent 

 which I have proposed, can really he an objection of any importance as re- 

 gards the navigation of the river, while the great object that would be 

 thereby gained by a farther depression of the road-way, to the extent of 18 

 inches, reducing its inclination to 1 in 40, instead of 1 in 24, as proposed bj 

 \\ alker and Burges, would he of the greatest advantage to the traffic 

 over the bridge, as well as to the effect of the new Houses of Parliament 

 when viewed from it ; a point which I submit ought not to he disregarded. 



Messrs. Walker and Burges state in their letter, as an objection to the 

 form of arch which I have proposed, that the failure, of one arch would 

 cause the destruction of all the piers and arches ; a consideration which 

 they say is not to be disregarded in a bridge, the piers of which have been 

 so badly founded, that to support them has been a constant expense, and is 

 at this moment a source of considerable anxiety: although they further 

 State, that the works they have in hand, if as successful as hitherto, will 

 render the piers much more secure than they have ever been ; they hope, 

 perfectly so. The part of this objection which is founded upon the lateral 

 thrust of arches, will apply with equal force to all arches of a segmental or 

 elliptical form, which are generally adopted in modern bridges, and even to 

 semicircular arches, of the lateral thrust of which I will not affect to sup- 

 pose Messrs. Walker and Burges to be ignorant, although in the allusion 

 which they make to Labelye's opinion that subject, they leave it to be so 

 inferred. With regard to the other part of the objection, namely, the failure 

 of the foundations, it may surely be assumed that Messrs. Walker and Bur- 

 ges would not have recommended the very serious outlay which is now being 

 incurred in securing them, if they conceived there was any risk whatever of 

 their ultimate failure; but if a possible failure is notwithstanding to be taken 

 into consideration, can a more powerful argument be advanced in favour of a 

 new superstructure, than that the weight upon the piers might thereby be 

 reduced at least one-third ? » 



To Messrs. Walker and Burges' design for a new superstructure I object, 

 principally because it does not accomplish the main objects for which a new 

 fuperstructure is, in my opinion, desirable, namely, the reduction of the mass 

 so the bridge, and the lowering of the road-way to the utmost practicable 

 extent ; neither does it afford any improvement whatever in respect of the 

 navigation of the river; the accomplishment of which objects is, in my 

 opinion, of far greater importance, both for the sake of public convenience 

 and architectural effect, than the style of architecture to be adopted. 



As to the principles which Messrs. Walker and Burges consider should 

 govern the nature of a design for a bridge over the Thames in London, 1 en- 

 tirely disagree with them ; I conceive that the height of the opposite shores 

 and buildings upon them should mainly determine the sesthetical character 

 of the design. If, as in Waterloo Bridge, where the shores are high, one 

 being naturally so, and the other raised, and the road-way is level ; where 

 the superstructure of a great public building like Somerset House is wholly 

 above the level of the road way ; and where the bridge groups with the 

 substructure of such an important building; the character of the design 

 cannot he too hold and massive ; but if, as at Westminster, w here the shores 

 arc low, and the bridge must in consequence group with the superstructure 

 of an extensive work like that of the new Houses of Parliament ; and w here 

 the parapet must, in consequence of the height required for the centre arch, 

 assume a curved line, which is an element rather of elegance than of bold- 

 ness, the character of the bridge should he light and graceful. 



I'pon the taste of Messrs. Walker and Burges' design for a new super- 

 structure in what they term the " Norman style," 1 forbear to offer any cri- 

 ticisms in detail, as the conditions which should be observed in a bridge 

 are, in my opinion, wholly at variance with the essential characteristics of 

 that stvle; nor do I consider it worth while to make any remarks upon their 

 observations relative to points of taste, including those especially which refer 

 to harmony and contrast between the bridge, the new Houses of Parliament, 

 and the neighbouring buildings, as they seem to me to furnish their owu 



In conclusion, 1 beg to add, that I still remain of the same opinion, as I 

 expressed in my report to the Fine Arts Commission, as to the necessity of a 

 new superstructure to Westminster Bridge upon the principles therein advo- 

 catl d; and as a favourable opportunity is now afforded of carrying into effect 

 that great public improvement, at an outlay, moderate, when compared with 

 its importance, I trust the Commissioners will not be indisposed to take my 

 recommendations upon this subject into their most serious consideration. 

 I have the honour to be, 

 Sir, 

 Y'our very obedient servaut, 

 32. Great IScorge Street, Charlks Barry. 



IfUhJvly, 1813. 

 The Rt. Hon. Chari.es S. Lkfkvre, 

 Speaker of the House of Commons, 



Chairman of the Commissioners of Westminster Bridge. 



OPENING OF THE NEW GRAVING DOCK AT WOOLWICH. 



The opening of this stupendous work took place on Monday. 17th July, 

 when this dock was entered for the first time by Her Majesty's frigate 

 iter, for the purpose of being coppered. &e. Viewed only as a work 

 of mere masonry and architecture, the dock would, in itself, be a most strik- 

 ing object; but when the difficulties required to he surmounted in its con- 

 struction are considered, it must be acknowledged that the new basin is an 

 object worthy of remark, and a specimen of the perfection to which this par- 

 ticular description of ei\il engineering is carried in this country. The basin 

 in question is of solid granite, with steps, or what are technically termed 

 .i.us. mi each side, 15 inches fo one foot deep, affording facilities for de- 

 ng to the bottom, and also for props or supports being affixed, thus 

 enabling any vessel, whatever may be her size, to be supported on her keel 

 without injury. The length is 300 feet at the top of the water, 245 feet at 

 the bottom ; the width of the basin is 80 feet at top, gradually diminishing 

 as the basin deepens. As it approaches the bottom it presents the appi . 

 ancc of a perfect concave some 26 feet deep. To this basin there are two 

 folding-gates, or locks, extending the whole width of the dock, made of 

 iron and timber doubled, and weighing about 60 tons each ; and the perfec- 

 tion with which these gates work, and are adjusted to each other, may be 

 seen in the fact, that though each of them are of the enormous weight of 60 

 tons, two men, or rather a boy and a man, can move them easily. These 

 gates open to the general basin communicating with the Thames. The dock 

 itself is filled by the river tide, or by a steam-engine working with two 

 20 horse boilers, which can either fill the dock or withdraw the water in 

 about six hours' time. When the engine is required to empty rhc dock, the 

 water withdrawn from it can either be discharged into the common sewer, 

 or into the basin, which communicates with the Thames The engine is 

 situated some hundred yards from the basin, is by Boulton and Watt, and 

 is a beautiful piece of mechanism. The time it takes to empty the dock 

 varies according to the size of the vessel received in it, a large ressi 1 dis- 

 placing more water than a smaller one. In the case of the Ckichetter, 

 which appeared to us to be of the size of a 46 gun ship, the time taken 

 was about six hours. There is also upon the top of the engine-bouse a 

 tank holding some 200 tons of water, available in cases of accident, and in 



