This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1851 edition. Excerpt:...In the Hexham Bridge, built under Smeaton's direction, the gravel bed, owing to the floods, which he thought were properly provided for', was removed from under the foundation of a pier, and the bridge fell down. A fine bridge at Plymouth, over the Lary, was found to be in imminent danger in consequence of the drifting away of the sandy bottom upon which the piers stood; and it became necessary to protect the bed with a layer of clay, and an overlayer of stone, for a distance of 60 or 70 feet on each side of the bridge (see fig. 68, D, E When the piles are thus driven in, the tops are cut off level, and the earth between them excavated for the depth of a foot, to admit a layer of broken stones, with lime and sand; upon the levelled pile heads a platform of oak, beech, or elm planking is laid, followed by a second laid across, and the whole strongly jointed; on this stage the masonry is commenced. The following figures showthe foundations of a pier of Lary Bridge, near Plymouth, which was set on a sandy bed; a layer of clay was placed on the sand between the piles A, A (fig. 68, 69), and above that a bed of rough stones a, a, and a series of sheeting piles B, B, inclosing the area; the tops of the piles being cut level, a caisson counteract the action of the water. The principal piles A A were 35 feet long, the depth of sand being very great; the sand was excavated by a large spoon for a depth of 3 feet between the piles, for the clay and rough stonework. A considerable portion of the work was done by the protection of a diving-bell in an admirable manner. was used to deposit the masonry, and in section; uppermost was another layef the flooring which it left for the courses of planks 3 inches thick (seen atV, is seen at bb, the lower...