thus neglecting the amount contributed by this tributary, and as the river was about an inch lower than when I measured the discharge of the Virginia channel, I have concluded it would be more exact to define the relative flowage of the two channels, thus: Ohio channel, 40 per cent.; Virginia channel, 60 per cent. Summing up these results, we see that of the two the Virginia channel at the coal-boat stage is about 1 foot deeper and 200 feet wider, and discharges three-fifths of the entire volume of the river. Were these the only considerations to be noted, it is manifest that the Virginia channel would unquestionably be the one to be chosen for the main channel of the river. The objections to this choice are the following:

On the Virginia side there are no local interests concerned in the possession of a navigable channel. The only town on that side is Williamstown, below the foot of Marietta Island. This is a place of so little importance that although I spent two weeks at Marietta, making the surveys, &c., no one from the Virginia side of the river made any representations to me on the subject.

On the Ohio side we have the flourishing town of Marietta, of 5,000 inhabitants, the citizens of which are unanimous in their opposition to the closure of their side of the river. The party that favors the retention of the Virginia channel and the stoppage of the other, is limited to a portion of the coal-boat interests of Pittsburgh.

The question of the present relative magnitude of the two channels, I consider to be of no importance, as either channel would be sufficiently enlarged by the current were the entire river to be turned into it, and the advantage would be rather with the narrower channel, which would necessarily deepen more than the other, in order to accommodate the increased flowage. The bars in the Ohio channel are formed by the sedimentary deposits of Duck Creek and of the Muskingum, and would be more readily removed by an increase in the volume of water than those in the Virginia channel, which are of coarse gravel. Were the river to be turned into the Ohio chute, there would be but little danger of the continued growth of these bars, as they are probably due to the present slackness of the current. It is so simple a matter to put the river into either channel, and to maintain it there, that I think we may entirely neglect the question of magnitude, especially as the difference is not great. The objections which the coal boatmen urge to the Ohio channel, are that it is narrower and more crooked than the other; that it is full of logs, and that they always use the other channel. The first objection amounts to but little. The map shows that the dif ference in curvature in the two channels is but slight, and that the width of the Ohio channel is more that twice that of the widest tow, and more than that of many other places that are habitually run without remark. River pilots are naturally conservative, and very unwilling to attempt new channels, but a few trips will probably remove their objections.

The only point that really deserves careful consideration is the complaint that the Ohio channel is dangerous from logs. This is a valid objection, experience having shown that hitherto there have been more obstructions on the Ohio side than on the other. Most of them seem to come from the Little Muskingum, with probably a few from Duck Creek. The former stream enters the river from the Ohio side, about two-thirds of a mile above the head of the island bar. It occasionally sends out snags which mostly lodge in the Ohio chute.

Believing that if this one objection were effectually removed, the coalboat interests would cease to oppose the closing of the Virginia channel, I made this statement to the mayor and council of Marietta, and

they at once hired a snag-boat and removed all the snags that could be found in the Ohio chute. They also, at my recommendation, sent parties of axmen up Duck Creek and the Little Muskingum to cut up and remove all snags, and trees likely to become snags, so that no more obstructions might be carried into the river from these streams. After making my first survey I went down to examine the dams below Cincinnati, and on my return I carefully examined the work done in the river, and found that the channel was entirely clear. Captain Rowley, the consulting pilot, examined the two tributary streams in a skiff, going up each about three miles, until a dam and rapids stopped him, and reported that except at one or two specified places the work was satisfactorily done. The snags and trees to which he called attention were at once removed, and I feel secure in reporting that there is no present or prospective danger from snags in the Ohio channel of Marietta Island. To make assurance doubly sure I requested the authorities of Marietta to guarantee the repetition of this work for five years. This they have done, as shown by the letter hereto annexed, and marked A. I have also called their attention to the dike extending downward from the foot of Marietta Island, which narrows the Ohio channel so much, that I was afraid that it might require removal. They have also agreed in the letters marked B and B1 to do this at their own expense, should the channel be kept up on their side of the island.

The commerce of Marietta is fully represented in the accompanying communication marked C, which the mayor informed me faithfully represents the present commerce of the place. The Marietta and Pittsburgh Railroad, a new enterprise, which at present only runs to the coal-mines of Morgan and Monroe Counties, distant about twenty-five miles, strongly protest against any closing of the Ohio channel. Their coal-landing has been placed just above the town, and they dread its sacrifice by a dam above. They also expect to do a large business in tobacco, lime, fire-clay, &c. If cut off from the river channel where they are now, they will be compelled to seek it above the head of Marietta Island, or traverse the town, cross the Muskingum River, and make a new landing in Harman. Their protest through their president, General A. J. Warren, is hereto annexed, marked D, as also a map of the road, marked D1. The question of closing one of the channels at Marietta Island has been agitated for the last thirty years, and is still a source of annoyance and dread to all parties interested. It is obvious that the river must be concentrated, and the parties in favor of either side can never be brought to agree. Í append a petition, marked E, of many steamboat men, urging the retention of the Ohio channel, and a similar one against it from coal-boat men, which I have marked F. There is no doubt in my mind that the closure of the Ohio channel will ruin the commerce of Marietta. Closed channels generally keep their depth above dams, but invariably fill up below them. When we add to this cause the amount of sediment brought down by Duck Creek and the Muskingum, which will no longer be swept away by a river current, we can see at once that there would be no chance left of keeping a channel open to the Marietta landing, nor to the railroad coal-landing above.

I conceive that nothing but the direst necessity can justify the deliberate destruction of a town of 5,000 inhabitants, the first settlement in the State, and that should it apparently be necessary to destroy the outlet which nature gave it, the Government ought to provide another at whatever cost. But in the case in question I cannot see that there is need of injuring any one. Marietta has removed all obstructions, and

has taken every precaution to prevent any new ones from coming, by cleaning out the streams that furnish them.

There is no sacrifice within their means which its citizens are not ready and willing to make, as they know that the value of all their property is at stake. They have done everything that I suggested, and promised everything for the future that I thought it just to ask, and in return I feel it my duty and privilege to strive to protect their rights, and in fact their municipal existence. The question must be settled now, as it is unbecoming the dignity of the Government of the United States to let it remain open any longer, to the prejudice of the entire river interests. Scarcely any work has been done on the river which some one has not at first opposed, and afterward acknowledged to have done good. It seems there is but one way in which this matter can possibly be settled, and therefore I earnestly recommend that I be allowed to build a dam across the Virginia side, a little below the head of the island. If speedy action is taken I may get most of it in before winter, as the stone has been ready for over a year. I would prefer locating the dam as far below the head of the island as practicable, in order to prevent the draught over the dam in high water from tending to draw boats out of the channel. This is a defect in dams made in the prolongation of an inland shore, and moreover their extreme length greatly increases their cost.

Respectfully submitted.

Brigadier General HUMPHREYS,

WM. E. MERRILL,
Major of Engineers.

Chief of Engineers, Washington, D. C.

K 3.

STEUBENVILLE, OHIO, December 1, 1870.

GENERAL: Your letter of instructions of November 18, and accompanying papers in relation to improving the Ohio River in the vicinity of Marietta Island, were duly received.

The board having visited the locality and examined the questions involved, are of the opinion that the low-water navigation requires a dam to be placed across one of the channels to increase the depth of water in the other. That the width and direction of the channels admit of either being selected, and that they do not differ essentially in their capacity to accommodate the river commerce. That the closing of the channel on the Ohio side of the island will be a serious injury to Marietta, a town of 5,000 inhabitants, while there will be no corresponding injury to any other interests by closing the channel on the Virginia side, of the island.

We therefore recommend the construction of a low-water dam on the Virginia side of the island, at such point across the channel on that side as the engineer in charge of the Ohio River improvement may select.

K 4.

APRIL 19, 1871.

GENERAL: The board of engineers appointed by your order, in accordance with section 5 of the act making appropriations for the improvement of rivers and harbors, approved July 11, 1870, have the honor to submit this their final report. They have already submitted two partial reports, the first of which discussed the Newport and Cincinnati bridge, (it is Appendix D of this report.) The second gave the project of a law for the future regulation of bridges over the Ohio River, with the reasons for the various specified provisions; (it is Appendix E of this report.) With this their third and last report, they believe that they have completed their duty in regard to the bridges built or being built over the Ohio River.

Before commencing the detailed discussion of the bridges over the Ohio, it will probably be advisable to state a few facts about the river itself.

The Ohio River is formed by the junction of the Monongahela and Alleghany at the city of Pittsburgh, and thence it flows in a general direction a little south of west to its junction with the Mississippi at Cairo. In its upper course, especially between Pittsburgh and Wheeling, it flows over a bed of coarse gravel and boulders, and sometimes of rock, which is but little liable to be moved by an increased velocity to the current. Below Wheeling the gravel becomes finer, the boulders fewer, and bars of river-sand appear. This condition of increasing fineness in the materials of the bed continues to the falls at Louisville. Below the falls the river changes very decidedly, assuming the character of a river with a movable bottom, which it maintains to its junction with the Mississippi.

The slope of the river-surface, at low water, varies in the same manner. The following are the average slopes: From Pittsburgh to Wheeling, (ninety miles,) 10.44 inches per mile; from Wheeling to Letart's Falls, (one hundred and forty-one miles,) 7.42 inches per mile; from Letart's Falls to Louisville, (three hundred and sixty-six miles,) 4.68 inches per mile; from Portland to Cairo, (three hundred and sixty-five miles,) 3.05 inches per mile.

The declivity of the river-slope at what is known as "The Falls of the Ohio," at Louisville, has been omitted from the averages given above. It is 25.7 feet in four miles. The entire length of the Ohio River is nine hundred and sixty-seven miles.

The widths of the river, as might be expected, increase gradually from its head to its mouth. The following are the widths between banks at various points:

In low water the river does not occupy the entire space between the banks, and at the bars it becomes very narrow. The following table shows its low-water width at several of the more prominent bars:

It will be observed that these widths increase gradually except at Four-Mile Bar. At this point the river is quite wide and shallow, and the bar is not well defined like the others, but partakes of the nature of a shoal. Were the volume of the river concentrated, the width would probably be about the same as at Rising Sun. At extreme low water, which, however, only occurs at irregular intervals, the depth on the bars is about eighteen inches above the falls, and about thirty inches below.

The greatest flood ever known on the Ohio, above the mouth of the Wabashi, was that of February, 1832. Below that point the flood of March, 1867, was the highest known, being 6 inches higher at Caseyville and 3 feet higher at Paducah. The following list shows the heights above low water of these floods at various points:

The only continuous records of the rise and fall of the Ohio that we have been able to obtain, are those at Pittsburgh, Wheeling, Cincinnati, and Louisville. The last three will be found in the reports on the bridges at those cities. As the bridges are discussed in the order in which they are met in descending the river, this is probably the most suitable place for giving the Pittsburgh record. The depth of water at Pittsburgh determines the departures of the coal fleets. The coalmines are all up the Monongahela, except a few along Saw-Mill Run, and the coal-barges come down one or two at a time through the locks and dams of the Monongahela slack-water. They accumulate in the harbor of Pittsburgh until there is 7 feet or more in the river, and then they are formed into fleets of from eight to twenty boats and barges, and are pushed down the river by powerful tow-boats. The steamer is always in rear of the fleet with about two-thirds of her length projecting behind.