“Mr. Thomas Wilson, Architect of the celebrated Bridge at Bishop’s Wearmouth, near Sunderland, furnished a design (5) for one of cast-iron, with stone piers, consisting of three large segmental Arches, the centre one being 240 feet span, and 65 high, and the two sides of 220 feet: the breadth of the road above was to have been 45 feet; and his estimate for the iron-work alone amounted to £55,061. See the ‘Third Report,’ pages 9 and 17, and Appendix C. page 76. A large engraving of the Elevation and Sections is also contained in the folio of Plans, &c. Plate viii. In section 4, article 9, page 14 of the ‘Report,’ the Committee appears to have given a preference to this design, with the side-approaches and improvements of the shores by other Architects; it being supposed that an ascent of about 2½ inches in a yard would have been sufficient for such a Centre Arch.
“The next three designs (6, 7, and 8,) were also confined to Iron Bridges, and were furnished by Messrs. Thomas Telford, Surveyor, and James Douglass, Engineer, of which only one was published. Their first idea was to diminish the ascent by increasing the length of the Bridge on the Surrey side, and by placing the largest arch nearest the City shore; its dimensions being 160 feet span, and 65 rise. Their estimate, including some extensive improvements along the banks of the River, amounted to £988,154; but this design was particularly objectionable, both on account of its unsymmetrical appearance, and the inconvenience of its navigation; and in their subsequent plans, therefore, they placed the great arch in the centre, without any other material alteration. The estimate for this was £1,041,654; but their chief design (9) was constructed on the principle of inclined planes gradually descending at the sides on to the wharfs at each end of the Bridge, and rounded for the convenience of carriages. The edifice itself was to be of iron, having an ascent of 2¼ inches in a yard, and was to consist of five arches decorated with statues, trophies, &c., commemorative of the Naval Triumphs of England, which were to give it the name of ‘Victory Bridge.’ The principal Arch was to be 180 feet span, and 65 high; and the lateral approaches were to be formed upon wharfs gained out of the River by embankments, and supported also by iron Arches, having warehouses beneath them. As a protection to the Bridge and its adjoining buildings, it was proposed that all the Arches, but the centre, should be closed at night by a chain; that in the spandrils of the great Arch, watch-houses should be constructed; and that the communications with the wharfs should be cut off by gates. The site of this Bridge was proposed to be the very line which the New one is now taking, and the estimate for it was £1,054,804: see the ‘Third Report,’ pages 8, 9, 17, Appendix B. 3, pages 57-73; and Plates ix.-xii. in the folio volume of Illustrations. The Report states that this plan would prove, in some degree, the most speedy and economical, and that it would interfere with existing buildings less than the former; though it is admitted that the turns to the ascent would be both inconvenient and dangerous.
“Mr. George Dance, Architect to the City, and Professor of Architecture in the Royal Academy, was the only person who at this time furnished the Port of London Committee with a design (10) for parallel Bridges with Drawbridges for the passage of vessels; and a single glance at the fac-similes of his drawings in Plates xiv-xix. of the folio of Plans, &c., will probably be quite convincing as to their inconvenience. The best idea of this peculiar design is, however, to be gained from a large coloured bird’s-eye view of the perfect edifice, drawn by the Architect, and engraven in aqua-tinta by Thomas Daniell, dedicated to Lord Hawkesbury, and published November 10th, 1800; a copy of which is in volume xiii. of Mr. Crowle’s Illustrated Pennant in the British Museum. It was intended to consist of two low level bridges, one on each side of the present; containing six elliptical Arches, having a drawbridge of two leaves in the centre of each, flanked by four round towers containing the mechanism for working them, and signal-staffs for flags, or reflecting lamps, to announce which of the passages was open. The space between the Bridges was to be 300 feet wide, furnished with mooring-chains, &c. &c., for securing the ships in tiers, so as not to interrupt the passage of smaller vessels. Each end of the edifice was to be formed into a grand semi-elliptical area, surrounding the Monument on the London side; and the estimate for executing the whole was £1,279,714; though Mr. Dance also sent in two more contracted plans, one amounting to £968,677, and the other to £807,537. In speaking of his Double Bridge, I should observe that he was led to the form of it by the great expense, steepness, deformity, and inconvenience attendant on an Arch high enough for the passage of vessels, which he explained in a Drawing marked Plate xiii. in the folio volume of Plans, &c. The inclination of Ludgate-Hill he found to be the steepest which he could adopt for an Arch of 60 feet, and that would have extended the approaches from East Cheap to beyond Union Street. The principal objections made to this plan were the great expense and delay connected with it; that the shipping moored in the basin would be exposed to a strong tide, with some danger; and that whenever their number was considerable, it would be difficult to provide for their uninterrupted passage, as well as for that of smaller vessels. For all these particulars, see the ‘Third Report,’ pages 9, 10, 17; and the Appendix D. pages 77-81.
“Such, then, were the designs laid before the House of Commons; and the Committee concluded its labour for the year 1800, by recommending the rebuilding of London Bridge of iron, with a centre Arch of at least 65 feet above high-water. It was advised, also, that the old edifice should remain till the new one were completed; the place for erecting which was opposite the West end of St. Saviour’s Church, as being the narrowest part of the River, and having buildings of the least value upon its banks, whilst the Northern end should form a street to the Royal Exchange. The removal of the Water-works was also recommended; and the funds for carrying these works into effect were proposed to be raised, firstly, by a Bridge-toll on horses and carriages, which, it was calculated, in 20 years would discharge a debt of £100,000; secondly, by a sum charged upon the Bridge-House Estates equal to their annual expenditure, which being taken at £4200, in 25 years would amount to £105,000; and, thirdly, £100,000 more were to be raised by an additional debt on the Orphans’ Fund: this sum of £305,000 being considered as more than sufficient for erecting Mr. Wilson’s Bridge, and making a proper compensation to the Water-works.
“Soon after the appearance of these resolutions, but too late for publication in the Committee’s Report, two other designs were presented, an account of which was printed in a Supplement to it. The first of these, see Appendix H. pages 143-147, consisted of a design by Mr. James Black, Civil-Engineer, (11) for a Bridge of Granite, with three elliptical Arches; the centre being 230 feet span and 65 high, and the sides having a span of 220 feet each: the inclination was to be 2 inches in a yard, and the estimate, £294,089: 6s. Two folding engravings, consisting of a Profile and Sections, will be found in Plates xxii.-xxiii. of the Supplementary Illustrations of the folio volume of Drawings.
“The other design (12) was by Messrs. Telford and Douglass,—see Appendix I., pages 148, 149,—for a cast-iron Bridge of a single semi-circular Arch 65 feet high, and 600 feet in the clear; the roadway being 45 feet wide in the centre, and increasing to 90 feet at each granite abutment, to strengthen the foundation, afford a greater space, and communicate better with the inclined planes. The estimate was £262,289, and a very large engraving of it by Lowry, comprehending an Elevation and Sectional Ground-plan, with another outline of the ribs and framing, form Plates xxiv. and xxv. of the Supplemental folio Illustrations.
“In consequence of this last design, the attention of the Committee was directed to the consideration of a metal Bridge with one Arch; and on their meeting in 1801, a series of Questions was transmitted with this last plan to Dr. Nevil Maskelyne, Astronomer Royal; the Rev. A. Robertson, Savilian Professor of Geometry at Oxford; John Playfair, Professor of Mathematics at Edinburgh; John Robeson, Professor of Natural Philosophy at Edinburgh; Dr. Milner; Dr. Charles Hutton, of the Royal Military Academy, Woolwich; Mr. Atwood of Knightsbridge; Colonel Twiss, of Woolwich; Mr. William Jessop, of Newark; the late Messrs. John Rennie and James Watt; Messrs. John Southern, of Soho, Birmingham; William Reynolds, of Coalbrook-Dale; John Wilkinson, of Bradley in Staffordshire; Charles Bage, of Shrewsbury; and General Samuel Bentham, Inspector General of the Naval Works of the Admiralty; whose answers for an Appendix to the ‘Report of the Select Committee’ for 1801: Nos. 1-16, pages 9-83. For the Questions themselves, see pages 4-7 of the Report; they were 21 in number, and inquired the nature of pressure and gravity in such a Bridge? whether it would be strengthened by increasing towards the abutments? how the weight should be distributed to make it uniformly strong? what weight it would bear? and what force would overturn it at any particular part? concerning the form of the Arch, and how to improve it? the importance of models and experiments? the means of keeping ships in the centre of the stream? the proportionate strength of the abutments? the possibility of constructing centering for it, without obstructing the ordinary navigation? the nature, power, dimensions, and method of casting the metal and cement to be employed? how the design might be improved and rendered more durable? and whether the estimates equalled or exceeded the execution of the works?
“It was probably the very great diversity of sentiment prevailing in the answers to these inquiries, which caused this design to be ultimately abandoned; for though its practicability, magnificence, and excellence, were universally admitted, yet there were so many doubts as to the actual strength and cohesion of cast-iron, the power of the crown of the Arch, the possibility of making the structure as one self-dependent frame, and of fortifying the haunches without overloading them, that few of the returns agreed with each other throughout. Drs. Maskelyne, Hutton, and Mr. Rennie, recommended an elliptical arch; Professors Robertson, Playfair, and Robeson, a circular one: some considered increasing the width of the roadway at each end of great importance; others proposed making it still wider; Professor Robeson thought it not very essential; and Professors Playfair and Robertson conceived that it took away from the strength of the whole. Dr. Hutton, Mr. Robeson, and Mr. Watt, supposed that the gravity of the Bridge would of itself be so great, that any additional weight would be trifling; and that the mast of a ship striking it, would break only that particular part, without damaging the rest, though repeated shocks might in time destroy it. For its construction, however, cast-iron of the soft-grey kind, or rather gun-metal, was generally preferred, as well as liquid iron for a cement; which some practical persons considered as not adapted for the purpose, and only advised the whole to be well fitted together. The papers of Col. Twiss and Mr. Watt recommended that the Bridge should consist of three arches; and with that of Mr. Southern was sent a drawing,—Plate xxvi. in the folio of Plans, &c.—of his method of more securely constructing the arch and frame-work.
“The return sent in by General, afterwards Sir Samuel, Bentham, see ‘Appendix,’ No. 16, page 76-83, instead of considering the lofty Bridge of Messrs. Telford and Douglass, was occupied by detailing a new design, (13) engraven by Basire, on Plate xxvii., in the folio of Illustrations. Its principal characteristic was an enlargement in the centre, into a sexangular form of more than twice its ordinary breadth, having in the middle an octagonal basin, spacious enough for a ship to lie in, without touching a Drawbridge constructed in each side; which Drawbridges were to be 30 feet wide, and so contrived, that either should be sufficient for a temporary passage; and the vessel having passed through one, it was to be let down and fixed, before the other was opened. The edifice itself was to be of granite, on a rise of an inch in a yard, and to have eight segmental arches, with the Drawbridge-passage in the centre, guarded by four low round towers for the machinery: the estimate was £210,411.
“The ‘Appendix,’ No. 17, pages 83-85, contains an additional paper from Mr. Wilson, giving a farther account of his design, and of a model which he had constructed of it; and concluding with an estimate of £163,496 for the whole work.