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“Should any alteration be made hereafter in the dimensionsor method of executing any part of the work, the extra priceor deduction, whichsoever it may be, shall be agreed upon bythe contractor and the county surveyor or surveyors, beforesuch part or parts of the work are put in execution. Butsuch alterations shall only be considered as affecting thematter or object thus specified, and not have any tendency toannul the general contract.

“The whole of the works are to be under the superintend-ence of the surveyor of the public works of the county ofStafford, or of such surveyor or surveyors, person or persons,as the justices assembled in quarter sessions shall at any timehereafter appoint. And should it appear, at any time duringthe execution of the works, that the contractor is neglecting,or doing any part contrary to the true spirit and meaningof this specification and drawings attached, then the magis-strates shall have it in their power to take it out of his hands,and employ any other person or persons to complete it ; andwhat money may remain due to him shall remain in thehands of the treasurer of the public stock of the county ofStafford till the whole work is completed; and any loss thatmay be sustained through the neglect or misconduct of thesaid contractor, to be paid for out of it.

“ The whole of the work must be delivered, fixed, and com-pleted, on or before the day of in the

year

“ The bridge was erected in the year 1830. The totalweight of iron-work, which was executed by the ColebrookDale Company was 340 tons.

The whole cost of the bridge was as follows:—

Iron-work, delivered, fixed, and completed.£3,800 0 0

Masonry. 3,193 0 0

Foundations, which were piled according tothe most approved method ; and the ap-proaches, which are of considerable lengthand height.:. 2,500 0 0

Total. £9,493 0 0

We come now to the erection of one of the most celebratedstructures in the world—the iron bridge over the riverThames — Southwark Bridge. This splendid work crossesthe water between London Bridge and Blackfriars. Thespot seems to have been well selected, and great improve-ments and alterations, particularly on the Surrey side, havetaken place in consequence of its erection. Southwark Bridgewas built in compliance with an act of parliament obtainedby a company of proprietors in the year 1811, but notwithout great opposition on the part of Sir William Curtis and others. The first stone of the south pier was laid byLord Keith, on the 25th of May, 1815, who, with the gen-tlemen of the committee of management, partook of a coldcollation on a temporary bridge erected on the works. Onthe 7th June, 1817, the Right Honourable Matthew Wood, asLord Mayor, laid the first stone of the northern abutment,and the works were then carried on with great energy. Thewhole was completed in something less than five years, andopened to the public at midnight, in April, 1819.

The arches of this gigantic edifice are of the largest spanof any known to exist. The soffits consist of solid masses ofcast-iron, of a depth similar to the voussoirs of a stone bridge,and exhibit the first instance in which such a bold plan hasbeen carried into effect. The middle arch rises 24 feet, witha span of 248 feet, and is 4 feet wider than the famous ironbridge at Sunderland. It is composed of eight ribs, rivetedto diagonal braces ; each principal rib being 6 feet deep atthe top of the arch, and gradually extending to 8 feet at theabutments, or parts that rest upon the stone-work. Its whole

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height above low-water mark is 55 feet to the roadway.The other arches are similarly formed ; the span of the twoside ones being 210 feet. The abutments are of solidmasonry, laid in radiating courses, with large blocks ofBramley-fall and Whitby stones. Vertical bond was adopted,running through every two courses at intervals, therebygiving to the whole mass a solidity perfectly immovable.

The masonry of the piers, in like manner, was carried upwith horizontal and vertical courses to the springing of thearches; from which points they radiate in a wedge-likeform. These piers are 60 feet high from the bed of theriver to the top of the parapet, and 24 feet in breadth. Thefoundations of this bridge were laid in coffer-dams, whichwere of necessity made very strong, from the irregularities jof the bed of the river at this spot. The dams were elliptical Iin form, and were constructed of three rows of piles of wholetimber. In the spaces occupied by the base of the masonryof the piers, a row of whole timber sheeting piles were drivenall round the outer edge of the offsets, making, as it were, asquare internal dam. These piles, while they formed a securebarrier to the foundations of the piers, acted as a powerful |auxiliary to the main dam in securing its base. The center- iings on which the arches were turned were of very ingenious |

construction ; and with such skill was the whole work j

designed and carried into execution, that the settling of thecentre arch was only 1 inch and 7-8ths. The bridge is 718feet long between the abutments, and 42 wide between theparapets. The width of the roadway is 28 feet, with footways7 feet wide on each side. The weight of metal in the centrearch is 1,665 tons ; in the side arches, 2,928. The totalweight of iron in the whole structure is stated to be about5,780 tons.

This noble bridge was designed and erected by the cele-brated Rennie. The whole of the iron castings were madeat the extensive works of Messrs. Walker and Company, at I

Rotherham, and there put into arches before being shipped j

to London . The massonry was executed by Messrs. Jolliffe j

and Banks . The cost of the whole, including its connecting j

avenues, amounted to nearly £800,000. j

Iron bridges had, about this time, also attracted the atten- jtion of the French engineers; and the following description of jthe Pont des Arts at Paris will be interesting, not only from iits being the first iron bridge erected in France , but also from iits presenting much novelty of design. j ;

The Pont des Arts was designed by M. de Cossart, the j ;inspector-general of roads and bridges, but some variations ' :were afterwards made from the original design by M. Dilon, ;to whom the execution of the work was intrusted. j

The bridge is a nine-arched structure, the width between |the piers measuring between 56 feet 9-^ inches, and the thick- Iness of the piers themselves, 6 feet 4^ inches above the foot-ings. Each arch consists of five ribs, 7 feet Ilf inches apartfrom centre to centre, each rib forming a large cast-iron arch, ,6§ inches in depth, and 3-ft inches in thickness, formed of thetwo beams meeting at the crown of the arch. The extremi- i

ties of the arch rest on skew backs of cast-iron, embedded in |

masonry at the top of the piers. The chord of the arc j

measures 60 feet 8f inches, and the versed sine 10 feet 8 j

inches. The smaller arches of iron are turned over the piersspringing from the haunches of the adjacent principal arches, j

and supporting the roadway above the piers. Upright sup- \

porters are carried from the centre of the piers to the crown j

of the small arches, and are strengthened by struts supportedon the larger arches. The ribs of each arch are bound jtogether by tie-rods fixed to the top of the large arches. At jfirst, the upright supports of the smaller arches were con- |nected by only one cross-piece, and had no braces in the |