The length of every pier is seventy feet, and each end is terminated with a saliant angle against either stream. The breadth of the two middle piers is seventeen feet at the springing of the arches, and contain three thousand cubic feet, or near two hundred tons of solid stone; and the others on each side, regularly decrease one foot in breadth, so that the two next to the largest are each sixteen feet, and so on to the two least next the sides, which are no more than twelve feet wide at the springing of the arches. The centre arch is seventy-six feet wide, and the others decrease in width four feet on each side, so that the two next to the centre arch are seventy-two feet wide, and so on to the least of the large arches, which are each fifty-two feet wide, and the two small ones in the abutments close to the shore, are about twenty feet in width. The foundation of the bridge is laid on a solid and firm mass of gravel which lies at the bottom of the bed of the river; but at a much greater depth on the Surry, than the Westminster side; and this inequality of the ground, required the heights of the several piers to be very different; as some have their foundations laid at five feet, and others at fourteen feet under the bed of the river. The piers are all four feet wider at their foundation than at the top, and are founded on the bottoms of the above mentioned wooden cases formed of the most substantial work, eighty feet in length, twenty-eight in breadth, and these timbers are two feet in thickness. The caisson or wooden case, in which the first pier was built, contained an hundred and fifty loads of timber; and forty thousand pound weight is computed to be always under water in stone and timber. [Illustration: _Westminster Bridge._ ] [Illustration: _S. Wale delin._ _B. Green sc. Oxon._ _Walton Bridge._] The materials are much superior to those commonly used on such occasions: the inside is usually filled up with chalk, small stones, or rubbish; but here all the piers are the same on the inside as without, of solid blocks of Portland stone, many of which are four or five tons weight, and none less than a ton, except the closers, or smaller ones, intended for fastening the others, one of which has its place between every four of the large ones. These vast blocks are perfectly well wrought for uniting; they are laid in Dutch terrace, and also fastened together with iron cramps run in with lead. All this iron work is however entirely concealed, and so placed that none of them can be affected by the water.