TRENTON BRIDGE, over the Delaware, about 30 miles above Philadelphia. See Plate DX. No. 2, Fig. 2. The first corner-stone of this bridge was laid on the 21st day of May 1804. The front of the abutment on the Pennsylvania side being 65 feet in advance from the bank, it was deemed prudent to make it thicker than the one on the opposite shore; accordingly this abutment is 50 feet in front and 18 feet thick, with the back supported by a hori zontal arch from its foundation.
The fronts of the abutments from the surface of the ground, and the ends, and about 40 feet of the wing walls above the banks, are carried up with cut stone in courses of range work, varying in depth as they proceed upwards from twenty to six inches, and battering half an inch in the foot: and although no ornament was sought for, this masonry exhibits a solidity of work, and neatness of execution, that reflects great credit on the workmen who con structed it. The cut stone in the abutments are all clamped together with iron clamps, as high as is presumed the ice or other floating substances will ever assail them; and in every tier of stone there are a number of branch clamps extending diago nally and crosswise the abutment, connecting the whole together. The interior is made up of large rough stone, many of half a ton weight and upwards, compactly filled in with smaller stone, and the whole laid iu good lime and sand mortar, and forming one entire solid mass of masonry. These abutments are 19 feet above the ordinary flow of the tide, 6 feet above the highest freshes from ordinary causes, and at least 4 feet higher than the water has ever been known to rise, from obstructions by ice on the bars below. Besides this, the travelling way is raised nearly 3 feet higher ; so that no injury can possibly be sustained in the wooden superstructure by any substances floating on, or carried down the river in the highest freshets.
The wing walls on the east side, at the distance of 60 feet from the front of the abutments, spread or splay 78 feet; and for the first 20 feet they run into the bank, are laid as deep as the foundation of the abutment, and 7 feet wide in the bottom. From
the end of the angle, they are continued in a paral lel line with each other, 103 feet farther, on a gra dual taper to 4 feet, where they terminate. The exterior of this masonry is battered N an inch to the foot, while the interior is rather more than perpen dicular; so that the filling has little or no pressure on the side walls, but will settle in perpendicular lines.
The wing walls on the west or Pennsylvania side, which are 85 feet in length from the front of the abutment, extend about 18 feet into the bank, and spread or splay 66 feet, being the width of the street leading to the bridge.
In laying the exterior courses of the foundations of the piers, great care was taken to select flat and long stones, running many feet into the body of the piers. On these, and throughout the whole interior, are laid large rough stone of vast weight, and the whole closely filled in with building stone. The depth of these foundations vary several feet in dif ferent parts of the piers, owing to the irregular sur face of the rock, (ill some places forming a pretty regular basin), and this is as an additional security against their being moved by ice, rafts, or other floating substances coming against them.
An offset of 6 inches is made on these founda tions, where the cut stone commences: the pier here receives its proper shape and dimensions, which in this place is 68 feet in length, and 22 in breadth, with the end up stream, of a semicircular form. The levelling up of the foundation, and all the cut stone, are laid in terras mortar. On the pier next to the Pennsylvania shore, three courses of cut stone are laid, rising above the founda tion to the height of 4 feet 7 inches. On each of the other piers one course only of cut stone is laid, of 20 and 22 inches in depth; in which situation ice and every other floating substance will run over them during the winter and spring seasons.