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HISTORY OF IRON BRIDGES.

TRACT 6.

As in some degree and nature related to the foregoingaccount of iron arches, properly so called, we may here adda few words, just to notice two ingenious works lately exe-cuted, being a kind of straight or flat arch, for an iron aque-duct, supported on pillars, carried over rivers. These were,both of them, designed by Mr. Thomas Telord, engineer,and executed under his direction.

The former was a small aqueduct of cast iron, the first fora navigable canal, which was constructed in the year 1195 ,on the Shrewsbury canal, near Wellington in Shropshire.It is 180 feet in length ; and the surface of the water in theaqueduct is about 20 feet above that of low water in theriver. The supporting pillars, in this case, are also of castiron. There are no ribs under the bottom plates, thesebeing connected with the side plates, shaped like the stonesin a flat arch, which is also the case in the second instance,at Pontcysylte. The iron work of this aqueduct was cast atKetley foundery, by Messrs. Reynolds.

The second instance was erected in the year 1805, at thePontcysylte aqueduct. It having been found necessary tocarry the Ellesmere canal across the river Dee, at the easterntermination of the vale of Llangollen, at the height of 126feet 8 inches above the surface of low water in the river,Mr. Telford conceived the bold design of effecting this bymeans of an aqueduct constructed of cast iron, supportedby stone pillars. These are 20 in number, including theabutments : the length of the aqueduct is 1020 feet, andthe breadth across it 12 feet. It has been in constant usefor the purposes of navigation ever since it was first opened,on the 26th of November 1805, and it answers every pur-pose perfectly well. The iron work was cast, and set up,by Mr. William Hazledine, of Shrewsbury. A small view ofthe elevation of this elegant structure is as here below.