33 by 16 feet. The other river-piers are similar in construction to the channel-piers but smaller. They are 60 by 23 at bottom, and 33 by 12 on top.

The grades and curvatures on this bridge and its approaches are as follows, commencing at the face of the abutment on the Ohio or northern shore:

The approaches on the Ohio side, commencing from the abutment and not including a long and high embankment, consist of six spans of Bollman deck-trusses, each span being 121 feet, making a total length of 726 feet. The trusses rest on piers whose dimensions on top are 21 by 7 and 24 by 7. They have the usual batter, and are founded upon three feet of concrete, at depths below the natural surface varying from 6 to 8 feet.

The approaches on the Virginia side consist of a great number of spans, some of which are both short and low-the authorities of Parkersburgh having objected to the construction of masonry arches. Commenc ing at the Virginia abutment they are as follows: seven spans of girder bridge, each 25 feet long; 4 spans of girder bridge, each 29 feet long; one through-bridge of 65 feet span over Market street; six Bollman deck-bridges, each 59 feet long; one Bollman deckbridge of 65 feet span, over Julian street; six Bollman deck-bridges, each 59 feet long; one Bollman-deck bridge, of 65 feet span, over Ann street, and eight Bollman deck-bridges, each 100 feet long, up to the first span over the river. The total length of the Virginia approach from the abutment is 1,994 feet. The piers for this approach vary in size on top from 10 by 4 to 18 by 8 feet. They are built with the usual batter, and the seven nearest the bridge proper rest on foundations of 3 feet of concrete, laid at depths of from 7 to 25 feet below the natural surface.

At the time of the surveys the water stood at 8 feet by the gauge of the Baltimore and Ohio Railroad at Parkersburgh. At this time the section of the river, at a point 900 feet above the bridge, was 15,676 square feet, and the discharge was 41,058 cubic feet per second, showing a mean velocity of 2.619 feet per second, or one and three-fourths miles per hour. The floats through the channel-span showed a velocity of 2.4 miles per hour. The actual water-way on the line of the bridge, at the date of the survey, was 13,749 square feet, which, being 12 per cent. less than the natural section above, showed that the average velocity of the water must be that much increased by the piers; it should be remarked, however, that the coffer-dams had not yet been removed, and the water-way was inore obstructed than it will be in future. The total high-water section at the bridge site is 114,854 square feet, of which 11,177 square feet, or 10 per cent., is occupied by the bridge-piers, and this would probably cause an increase in the mean velocity at that stage of the same amount. The low-water section is 7,271 square feet, of which 608 square feet, or 8 per cent., is obstructed. This, however, would cause no injurious effect.

The losses at this bridge up to date, as reported in Appendix B, amount

to $45,900. As the pilots become more familiar with the bridge these losses will probably nearly cease. That they should altogether cease is improbable, as winds, smoke, fogs, and accidents to machinery will still combine to occasionally cause collisions, which, however, must be considered as the irremediable dangers that will always attend river navigation.

The board have no changes to recommend in this bridge, which, like the one at Bellaire, has been admirably built, and with the most liberal care for the interest of navigation. It is a possibility that in the future it will be found that the main spans of these bridges are too narrow. Should that prove to be the case, we think that any changes that may subsequently become necessary should be made at the national expense. The total cost of this bridge, as reported by the chief engineer, James L. Randolph, has been $1,223,550.

NEWPORT AND CINCINNATI BRIDGE.

This is a combined railroad and highway bridge, crossing the Ohio River about one mile above the Covington and Cincinnati suspension bridge, and connecting the cities of Newport, in Kentucky, and Cincinnati, in Ohio. It belongs to a bridge company, and is being constructed under the authority of the joint resolution of March 3, 1869, (Appendix A,) which is supplementary to the act of July 14, 1862.

This bridge was in process of construction as a "low" bridge, with a draw 70 feet above low water, but the Forty-first Congress, in its third session, ordered that the bridge be raised to 100 feet above low water, as recommended in our report to the Chief of Engineers dated December 21, 1870, which has been printed as Executive Document No. 22, of the third session of Forty-first Congress. For a detailed description of this bridge and of the changes recommended, reference is made to that document, which, corrected for typographical errors, is submitted again (see Appendix D) as a part of this report.

In recommending that this bridge be raised, and in estimating the cost of doing so, we did not feel at liberty to change its alignment, though there was no reason why the company should not do so, if they thought best. The change has been so recently ordered that it is yet uncertain what changes in the location of the approaches may be adopted, and therefore we have nothing to add to our previous report. Any modification of the Cincinnati approach, however, is an unimportant matter to navigation, as probably no change will be made in that portion of the bridge which spans the river. The losses by collision with the piers and coffer-dams of this bridge amount to $4,000. (Appendix B.)

COVINGTON AND CINCINNATI SUSPENSION BRIDGE.

This is a highway bridge, owned by the Covington and Cincinnati Bridge Company, and connecting the city of Covington, in Kentucky, with the city of Cincinnati, in Ohio. It was commenced in 1856, and the two piers were raised to the level of high water. The financial crisis of 1857 caused a stoppage of the work, and it was not resumed until 1863. From that time forward the work of construction progressed rapidly, and the bridge was finally opened to travel on the 1st of January, 1867, eleven years after the foundations were begun. It is a magnificent structure, and one of which the citizens of the two cities are justly proud.

This was the second bridge actually begun over the Ohio River, and it will be instructive to indicate the course of legislation in regard to its height and span.

The first charter was granted by the State of Kentucky, in February, 1846, with no restrictions as to height or span, but a proviso prohibiting the erection of any bridge "which may obstruct the free and common navigation of the said river Ohio." This charter was confirmed by the State of Ohio in March, 1849, with the additional proviso "that the said bridge shall not be of less span than 1,400 feet, nor of less elevation at the center of the river than 112 feet above low-water mark." In March, 1856, the charter of the bridge company was amended by the State of Ohio so as to permit a span of 1,000 feet, but the height at the center was increased to 122 feet. In January, 1863, the State of Kentucky authorized a reduction of height at the center to 100 feet above low water, and in March, 1863, the State of Ohio concurred in this reduction. In March, 1865, the State of Ohio passed a general act authorizing the construction of bridges over the Ohio River, Provided, "That the span of any such bridge be not less than the Ohio River at the point where the same is located, at low-water mark, and the height of any such bridge in the center shall not be less than 100 feet above the surface of the water at low-water mark."

The Covington and Cincinnati bridge was declared by act of Congress. approved February 17, 1865, (Appendix A,) to be a lawful structure when completed in accordance with the laws of the States of Ohio and Kentucky.

This bridge comes under the class of "high" bridges with continuous spans. It is built on the suspension plan, being supported by two large wire cables, strengthened by stays, and stiffened by iron girders and trusses. For a full description of the details, most of which must necessarily be omitted here, reference is made to the report of John A. Roebling, the engineer-in-chief, dated April 1, 1867. The roadway is 20 feet wide, with two side-walks outside of the cables 7 feet in width, making the total width of the bridge 36 feet. Between the abutments, the entire length of the bridge is 1,619 feet. The highest point of its under-surface is at the middle of the bridge, and at the time of our survey it was 1034 feet above low water, and 40% feet above highest water. These distances correspond to a mean temperature of 60°, and they are increased or diminished one foot by the cold of winter or the heat of summer. At this mean temperature, it has a clear headway of 100 feet above low water for a width of about 450 feet in the middle. The bridge consists of one main span and two half spans on either side. The southern side of the Cincinnati pier is located 35 feet north of the low-water mark, and the center of the Covington pier is 1,057 feet south of the center of the Cincinnati pier, with its river side 30 feet south of the low-water mark, there being between them a clear opening of 1,005 feet. The river side of the base of the Cincinnati pier is 18.8 feet above low water, and of the Covington pier 17.1 above. The width of the river between the piers at dead low water is 940 feet. Both piers being thus out of water at low water, the velocity at this stage is not affected by the bridge. The side spans have each a clear width of 255 feet between abutments and piers. The bridge approaches commence at Front street in Cincinnati, gradually rising on a mass of masonry 160 feet in length, to Water street, (66 feet wide,) which is crossed by a bridge of plate girders strengthened by wire-rope hog-chains. Between Water street and the wharf, a distance of 104 feet, the roadway rests on a solid mass of masonry, which also serves as an anchorage for the cables. Then

come in succession the Cincinnati half span, the main span, and the Covington half span to the Covington abutment. From this abutment to Second street is a mass of masonry, which also serves as the anchorage for the cables on the Kentucky side. The distance between the face of this abutment and Second street is 300 feet. On the Cincinnati side the foot of the approach on Front street is 2 feet below extreme high water, but on Second street in Covington it is 83 feet above.

Each pier is 82 by 52 feet at the base, and rises to the height of 913 feet above low water in one mass, solid under the towers, but hollow between them. Above this level begin the separate towers for the two cables, which are united near the top by a masonry arch, whose crown is 75 feet above the floor, with a span of 30 feet over the opening between the towers for the roadway. Including the ornamental turrets on top, the heights of the towers are 230 feet above low water, and 1673 feet above high water of 1832, the greatest flood known on the Upper Ohio. The foundations of the Cincinnati pier rest on a bed of compact gravel 12 feet below extreme low water. The rock bottom of the river was found to be 12 feet lower, but it was deemed unnecessary to excavate to that depth.

The foundations consisted of twelve courses on the river side, and eight courses on the land side of 12 by 12 timber, well bolted together, breaking joints, with the alternate layers at right angles. Interstices were filled with gravel and broken stone well grouted with cement. The timbers were from 25 to 40 feet in length, and the platform was 110 feet long by 75 feet wide. In each pier there is 400,000 cubic feet of masonry, and the weight on each square foot of the foundations, including the weights of the superstructure and of the loads, is 3.88 tons. The foundation of the Covington pier is laid on a stratum of mixed sand and gravel 6 feet below low-water mark, the solid rock being 11 feet deeper. Seven courses of timber were laid in this pit in the same manner as on the Cincinnati side, and on the platform thus formed the pier was built. Between each pier and the low-water mark, the surface was protected by a sloping riprap. This, however, does not obstruct the channel, as it is on the same slope as the wharves. Special care was given to the Covington riprap, which was bound together by a strong crib-work with a sunken flatboat at its foot.

The river at the site of the bridge has a width at low water of 940 feet, and a cross-section of 6,526 square feet. At 6 feet above low water (the stage at the time of the survey) it had a width of 950 feet, and a crosssection of 11,940 square feet. At both of these stages the piers were out of water, and the river was entirely unobstructed. At a stage of 18.8 feet, the water reaches the nearest side of the Cincinnati pier, and at 17.1 feet the nearest side of the Covington pier. At extreme high water the section is 80,475 square feet, of which 5,500, or 63 per cent., is obstructed by the piers. The mean velocity at that stage would therefore be increased in this proportion by the bridge. The grades on the bridge and its approaches vary somewhat on account of its arched shape. The heaviest grade is on the half spans, being 5.36 per 100, or 1 in 183, for a distance of 280 feet. On the main span the grades are much less.

The following tables of the stage of water during the last twelve years have been compiled from the official records kept at the Cincinnati waterworks. The first table is the same as that heretofore published in our special report on the Newport and Cincinnati bridge, excepting that the headway refers to the suspension bridge. The other table, showing the longest duration of the higher stages, is compiled from the same records, and has been added to supply a deficiency that was felt during the debate on the alteration of the Newport bridge.