Harlem River, or High Bridge.*

The width of the river at the place where the aqueduct line crosses it, is 620 feet at ordinary high water mark. As has been before stated, the shore on the southern side is a bold rock rising from the water's edge, at an angle of about thirty degrees, to a height of 220 feet. On the northern side, a strip of table-land forms the shore, and extends back from the river 400 feet to the foot of a rocky hill, which rises, at an angle of about twenty degrees to a few feet above the level of the aqueduct. The table-land is elevated about thirty feet above the river; the channel of the river to which the water is reduced at very low ebb tides, is 300 feet wide, and the greatest depth sixteen feet. Each side of the channel the bed is a deep mud, covered from three to four feet at ordinary flood tide. Next below the mud there is a thin stratum of sand, and this followed by a stratum of sand and large boulders intermixed. Below the stratum of boulders, or detached rock, there has been found, in the coffer dams for two piers, Nos. 8 and 9, a compact marble rock, and in the coffers for Nos. 7 and 10, a stratum of clay and sand, that is quite impervious to water, and affords a good medium for piling.

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Harlem River, or High Bridge.* The reader is reminded that this description was written previously to the completion of this most important work. Since then it has been finished in accordance with the original plan. Its beautiful yet massive proportions are themes of admiration with the thousands of persons who annually visit its romantic location. While the work was in progress, a branch, leading from one of the mains which crossed the river at the base, was converted into a gushing fountain; thus adding another charm to those with which the place was already invested. More recently an iron stair-way has been constructed on New York island, leading from the summit of the bridge to its base, affording increased facility to visitors. The annexed inscription is from the southerly face of the bridge:__

"Aqueduct Bridge, Begun in 1839. Finished 1848.

 

Water Commissioners Stephen Allen, Saul Alley, William W. Fox, T.T. Woodruff, Charles Dusenbery,

Engineers. John B. Jervis, Chief, H. Allen, Prin. Assist. P. Hastie, Resident, E.H. Tracy, Assist.,

Contractors. George Law, Samuel Roberts, Arnold Mason.

The general plan of the bridge is as follows: Across the river there are eight, arches, each of eighty feet span, resting on piers that are at each extremity and in the centre twenty feet wide at the spring line of the arches; with intermediate piers that are fourteen feet wide at the spring line; on the south of this range of large arches there is one arch, and on the north six arches, each of fifty feet span, resting on piers seven feet wide at the spring line, and two abutments that terminate the arch work of the bridge. From the abutments a continuous foundation wall of dry stone work is extended to the gate chambers on each side.

The whole length of the bridge is 1450 feet; the height of the river piers, above high water line, is sixty feet to the spring of the arches, and ninety-five feet above the lowest foundation that has been put down; the arches are semicircular, and the height 100 feet to the soffit, or under side, at crown; to the top of the parapets 114 feet above the ordinary high water line of the river, and 149 feet above the lowest foundation of the piers that have been commenced. The width across, on the top of the parapets, is twenty-one feet; the exterior of piers, spandrels, and parapets has a bevel of 1 in 48, and have openings in the interior walls.

The space between the parapets is arranged to receive and protect from frost two cast-iron pipes, each four feet in diameter, which are to lie twelve feet below the grade line of the aqueduct, to which they will descend from the gate chambers at the ends of the bridge. The object of using pipes in this case, is more effectually to secure the conduit from leakage, that might eventually injure the masonry of the bridge: and it incidentally allows the bridge to be constructed of less height.

Receiving Reservoir

This reservoir is 1826 feet long and 836 feet wide, and including its embankments, contains 35,05 acres, and its area at top water line, thirty-one acres, divided into two divisions. The northern division is designed to contain twenty feet depth of water, and the southern thirty feet in depth. But they are not fully excavated in some parts , where rock occurs, it not being deemed sufficiently important to incur the expense of excavation in rock for the increased capacity that would be obtained. the reservoir has a capacity for 150,000,000 imperial gallons, as it now stands. The reservoir is formed with earth banks, the interior having regular puddled walls to render them impervious to water; the outside protected by a stone wall, laid up on a slope of one horizontal to three vertical, the face laid in cement mortar and the inside dry. The inside is protected by a dry slope wall, laid on the face of the embankment which slopes one and a half horizontal to one vertical. The embankments are raised four feet above the top of water line, and are eighteen feet wide on the top, excepting the high banks on the southern division and the western bank on the northern division, which are twenty-one feet wide. The greater part of the embankments for the northern division are of moderate height; but a portion of the eastern and western banks of the southern division are thirty-eight feet high above their base. Vaults or brick archways are constructed, in which iron pipes are laid, so arranged that the pipes from the northern division connect with those from the southern division, and thence pass off to the distributing reservoir, and to supply the adjacent districts. The main vault is on the eastern side; it is 540 feet long, and is sixteen feet span; that on the western side is 400 feet in length, and eight feet span; designed for supplying, at a future day, the district on the North River side above Forty-second street. The pipes are all provided with stop-cocks, and so arranged that they can receive the water from either division; except one pipe from each division, that leads to the distributing reservoir. It is intended to carry three lines of pipes, each three feet diameter, to the distributing reservoir (at present only two lines are put down), and the arrangement will allow two pipes to be drawn from either division, so that in the event of emptying one division for repairs, the other would supply two pipes for the distributing reservoir, and all other pipes having a connection with each division would be in full supply, notwithstanding the suspension of one division. A pipe is put through the division bank, with a stop-cock, to allow the water or not, as may be desired, to pass from one division to the other.

The aqueduct intersects the reservoir at right angles with its westerly line, and 252 feet south of the north-westerly corner.

At this point a gate chamber is constructed, with one set of gates to pass the water into the northern division, and another set to pass it into a conduit of masonry constructed within the embankment of the reservoir to the angle of the southern division, where it enters by a brick sluice into this division. This arrangement gives the power of directing the water into either division, or both, at the same time, as may be desired.

In the division bank, a waste weir is constructed to carry off the surplus water from either division, when it rises to the proper height.

Distributing Reservoir

This reservoir occupies the highest ground in the vicinity, and higher than any part of the city south of it; the site is generally known as Murray Hill.

In order to maintain the elevation of the water, it was necessary to raise the walls of the reservoir to an average height of forty-five feet, and a half above the grade of the streets that bounded it on three sides; the greatest height being forty-nine feet, and the least, thirty-nine feet; the foundations were sunk five feet below the grade of the streets. The walls are of hydraulic stone masonry, constructed with openings, to reduce the quantity of masonry and give a more enlarged base.

The openings are made by an exterior and interior wall, connected at every ten feet by cross walls; which are carried up to within seventeen feet of the top, and there connected by a brick arch thrown from one to the other, and the spandrels between them leveled up solid, and a course of concrete put over the whole, six inches thick, which reaches a level ten feet below the top; whence the exterior wall is carried up single to the top.

The exterior wall has a bevel of one to six, and is uniformly four feet thick from the bottom to the top of the connecting arches; the inner wall is carried up plumb, with offsets, the lower section six feet thick, the middle section five feet, and the upper section four feet thick. The space between the exterior and interior walls, at forty-one feet below the top, is fourteen feet, or twenty-four feet from the outside of exterior to inside of interior walls; and the space between them at the spring of connecting arches in consequence of the bevel of the exterior wall, is reduced to nine feet and nine inches, and from outside of exterior to inside of interior walls, 17.75 feet.

The cross walls are four feet thick at bottom, and have one offset of six inches on each side, at eight feet below the spring line of connecting arches; they have an opening six feet high, and one foot and a half wide, at a suitable level near the bottom, to allow a drain to be formed, to collect any water that may leak through the work, and carry it off in sewers provided for that purpose, and also to allow persons to go in and examine the work.

Some modifications in the cross walls are made to accommodate the gate chambers, and connect the corners of the work. On each corner of the reservoir, pilasters, forty feet in width, are raised, projecting four feet from the main wall, and in the centre, on the streets and Fifth avenue, there are pilasters sixty feet wide and projecting six feet from the wall. The pilaster in the centre, on the Fifth avenue, rises seven feet above the main wall, and all the others four feet above. Doors are placed in the central pilasters on Fortieth and Forty-second streets, which give access to the pipe chambers, to work the influent and effluent stop-cocks, from which chambers an entrance is made to the openings in the walls.

In the central pilaster on the Fifth avenue, an entrance is made by a door to a stairway that leads up to the top of the walls. On the outside walls an Egyptian cornice is laid, which accords with the general style of the work. The pilasters are laid in courses, and well-dressed ashlars face, and the main wall with coursed rubble work, rough hammer-dressed. Inside of the walls of masonry, a thorough puddled embankment of suitable earth is formed, fifty-eight feet and a third wide at the line of reservoir bottom, and sloping on the inside face one and a half to one for twenty-four feet high, and one to one for the remaining sixteen feet high, and making, with the walls on top, a width of seventeen feet; the faces of the banks are lined with a course of rubble hydraulic masonry fifteen inches thick, and coped with dressed stone. The bottom is a very impervious hard-pan, on which two feet of puddled earth is laid, and this covered by twelve inches of hydraulic concrete. The reservoir is divided into two divisions by a wall of hydraulic masonry, at the toe of which a sloping bank of puddled earth is raised eighteen feet high and covered with rubble masonry; this wall is nineteen feet thick at the bottom, six feet and two-thirds thick at top water line, and four feet at top. In this wall a waste weir is placed, with a well of two falls, together fifty-two feet, from which the waste water enters a sewer in Forty-second street, and passes off about one mile to the Hudson River. In each division there is a waste cock to draw the water from the bottom.

The reservoir is designed for thirty-six feet of water, and when full will stand 115 feet above mean tide. The walls rise four feet above the water line. An Iron railing is to be placed around the walls on top of the cornice. The capacity of this reservoir is 20,000,000 imperial gallons.