566

HISTORY OF ENGINEERING.

Book J.

iron plates. The original plans for this undertaking were made by Mr William Jessop .This canal unites the Severn, Dee, and Mersey, and consists of a series of navigations,commencing from the river Dee, in the Vale of Llangollen, passing near Ellesmere,Whitchurch, Nantwich , and Chester , to Ellesmere Port , on the Mersey, in one direction ;through the middle of Shropshire , towards Shrewsbury , on the Severn, in another ; and ina third, by the town of Oswestry to the Montgomeryshire Canal at Llanymynech ; thewhole length, including the Chester Canal, being 103 miles. An act of parliament was ob-tained for this work in 1793. Mr. Telford was employed, and it was the occasion of hisattention being more particularly called to the study of civil engineering.

Ellesmere Port , on the Cheshire side of the Mersey, is 12 miles from Liverpool; here thecanal commences ; from thence to Chester is 9 miles, and from Chester to Nantwich 20miles. For the whole of this distance the locks will admit barges whose beam is 14feet. The perpendicular rise from low water in the Mersey to Nantwich is 177 feet.

From Nantwich to Whitchurch is 16 miles, with a rise of 132 feet; from thence to

Ellesmere, Chirk, Pont-y-cysvllte, and to the river Dee 1} miles; above Llangollen (in-cluding the Prees branch) the distance is 38$ miles, and the rise only 13 feet, in all 322 feetabove low water at Liverpool. About 3^ miles west of Ellesmere, at Francton, the canaldescends 30 feet, and from thence passes on a level to Weston Llulling fields in onedirection, and in another 10$ miles to Llanymynech, with a fall of 19 feet, where it joinsthe Montgomeryshire Canal.

The greater part of the fifty-one locks are only calculated for boats of 7 feet beam. They

are of tlie usual form, but the gates artlower gates, which are intwo leaves, have castheads, heels, and ribs inseparate pieces, withHandles, which are fast-ened together with nutsand screws ; the whole isthen covered with woodenplanking. The price ofthe lower pair of gates soformed in locks, with arise of 8 feet 6 inches,was 102/., and for the

chiefly of cast-iron.

For locks of 14 feet beam, the

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Fig. 545.

CAST-IRON LOCK ; I’LAN AND SECTION.

upper gates, where each valve was cast in a single piece, 59/. 10s. : at this time iron wascomputed at 14/. per ton delivered. These gates show nosymptom of decay, even at the present day.

Cast-iron Locks opposite Beeston Castle, Cheshire .

Here are two locks rising 17 feet, built entirely with cast-iron upon a stratum of quicksand : they answered thepurpose admirably, and, for this peculiar and difficultfoundation, were the best that could be adopted, thoughthe cost in the first instance was considerable. Fig . 54e - section OF lock.

The aqueduct over the valley of the Ceiriog, between Chirk Castle and the village, is710 feet in length ; the surface of the water in the canal is 70 feet above the level of that

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Fig. 547. AQUEDUCT OVER THE CEIRIOG.

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of the river below. There are altogether 10 arches, each of 40 feet span ; the total breadthat the top is 22 feet, that of the water is 11 feet, and the depth 5 feet.

The piers are 33 feet in depth, and 13 in width, or a little less than a third of the span ofthe arches which rest on them; these are all constructed in stone, and in the spandrills arelongitudinal walls, supporting the cast-iron plates which form the bottom of the canal.These plates have flanges cast on their edges, and are united by means of nuts and screws ;on these the sides of the canal, which are 5 feet 6 inches thick, are built with ashlarmasonry, backed with hard burnt bricks laid in Parker’s cement; the outside was facedwith rubble stone-work, like the piers and arches.

Under the towing-path, and beneath the gravel, a thin bea of clay was laid, and the outeredge protected by an iron railing ; the iron bottom plate forms a continued tie, and preventsthe walls from splitting. This work was completed in 1801, at a cost of 20,898/. ; thewhole, with the exception of quoins, coping and lining the sides of the water-way, which isof ashlar masonry, is of rubble work laid in good lime mortar.