458

HISTORY OF ENGINEERING.

Book I.

use and employment and wear and tear, or the purchase (as such engineer mayexpedient) of such engines, dams, and works as the said principal engineerproper to be retained shall be estimatedand determined by the principal engineer,and shall be paid or allowed to the con-tractor, his executors or administrators, to-gether with such sum of money as he orthey shall be entitled to in respect of thepart of the works which shall have beenexecuted.

“ The direction, certificate, valuation,and opinion of the principal engineer re-specting the execution of the works, thequality of the materials employed, thevalue of the works executed, any alter-ations or variations from the plans andspecification hereinbefore mentioned or re-ferred to, or of any part of the works whichshall have been executed, or of any engines,dams, machinery, or materials, or the con-struction of any matter, clause, and thingcontained in the contract, specification, orscale of prices, or either of them, or other-wise, respecting the premises, shall be finaland conclusive on the contractor withoutreference to any other party or partieswhomsoever.”

This splendid bridge, which has not itsequal in the world, reflects the highestcredit on all concerned in its erection, and,as long as it majestically spans the Thames,will be considered a masterpiece of con-struction. It. was opened to the public onthe 1st of August, 1831, with great pomp,after having been in progress seven yearsand three months.

The general depth at which the found-ation of the piers is laid below low water isabout 29 feet 6 inches, and the total quan-tity of stone used in constructing thebridge and its abutments was 120,000 tons ;the number of piles of 20 feet in lengthunder the piers and their abutments was2092, and the total number for the coffer-dams 7708. There were four sets of timbercentres, each weighing on an average 800tons.

The amount of Messrs. Joliffe and Bank ’sestimate for the bridge alone, including anextra set of centres, was only 425,081/. 9s. 2 rf.,the remainder of the sum previously men-tioned being swallowed up in the purchaseof land, houses, compensations, and law ex-penses.

Staines Bridge is a very beautiful struc-ture of five segmental arches of equal span,with a smaller through the abutments,which serve for the use of the towing-horses; it was completed in the year 1832,under the directions of Mr. George andSir John Rennie , sons of the eminent en-gineer to whose works we have alreadyalluded.

The span of each arch is 74 feet, andthe versed sine 9 feet 3 inches; the dia-meter of the circle of curvature at thevertex is 156 feet, and the height of the key-stone is 3 feet.

think

shall

most

think

Fig. 400.