able to make better progress. The whole country is now flooded with the excessive rains of last week, but a few days of dry weather will enable us to move again."

Mr. Stuntz has been employing about fifteen men and two yokes of oxen. Expenditures up to August 31 about $2,000. Accompanying this report is a map of the road, on a scale of 6 miles to an inch.

BRIDGE CONNECTING ROCK ISLAND ARSENAL WITH DAVENPORT.

Orders were received by me to proceed to Davenport and take charge of this work on the 13th of July last, and give my earnest attention to it. This I have done.

The laws and resolutions providing and making appropriation for this bridge required it to be for a double-track railroad, and wagon road above the railroad, and limited the cost of the bridge to $1,000,000, the averred estimate of the Rock Island Arsenal Commission. We probably cannot build such a bridge with this amount of money, and some modification of the law will have to be made by Congress, either changing the plan to a single-track railroad or increasing the limit of its cost. It is believed it is a mistake to say the commission made an estimate for such a bridge.

I have learned that a plan was submitted to the commission by Mr. Johnson, chief engineer of the Chicago, Rock Island and Pacific railroad, for a single-track railroad 16 feet wide, and a wagon road alongside, over the main river, 17 feet wide in the clear, but with no sidewalks, which bridge was to have a draw, on the pivot principle, giving two clear openings of 160 feet each; the whole to cost $1,296,292 11, from where it left the present railroad track on the Illinois side to where it joins the present track on Fifth street, in Davenport. Of this sum $1,046,317 58 was for the part over the main river, connecting Rock Island with Davenport.

When this plan was considered by the commission, objection was found to the inadequate width of the wagon way, which, it was thought, should be as great as 26 feet, with two sidewalks of 6 feet each. This would so increase the width of the pivot pier that the proposition was made to put the wagon way on top. This width of highway allowed room for a double railroad track, and this was recommended by the commission. I cannot learn that any estimate whatever was made for this enlarged bridge, but having Mr. Johnson's first estimate in my possession, and applying the same scale of prices to such parts as would be increased by the change, I find the double-track railroad, and enlarged wagon way, and sidewalk across the main river, would cost $1,785,142 67, and for the whole bridge, making connection with the existing track, $2,121,526 82.

It would then be clear, in my mind, that the commission in adopting the plan for a double-track railroad and highway 38 feet wide, (including sidewalks,) did not mean to adopt an estimate made for a single-track railroad and highway only 17 feet wide.

But in the agreement made by General J. M. Schofield, as Secretary of War, with John F. Tracy, president of the Chicago, Rock Island and Pacific Railroad Company, subsequent to the action of General Schofield as chairman of the commission, it is "provided that the aggregate cost of the said bridge shall not exceed $1,296,292 11, the estimate made by the commission appointed under the act approved June 27, 1866." As this sum is exactly that of Mr. Johnson's for the single-track railroad and narrow wagon road, it would seem that that must be what the commission estimated for.

In accordance with the directions received from you, I have designed the piers so that either bridge can be put on them as Congress may direct, and the work of construction is now in progress. The contracts for the masonry had all been made by General Rodman, and under these, according to my plan, will cost about $175,000. The piers are to be 36 feet by 7 feet on top, batter down stream, starting a semicircle in horizontal section. Up stream starting horizontal section to be two circles intersecting at the point, and tangent to the sides of the pier; described with radii equal to the width of the pier at the section, the slope of the line of the cutwater is one to one. The piers admit of two trusses being put upon them, giving a clear space of 28 feet. I have made the design so as to put the wagon way under the railroad. The railroad has an elevation on Mr. Johnson's plan 36 feet above low water. I have placed the wagon way 30 feet above low water, and raised the railroad track so as to give 12 feet headway, which is sufficient for the wagon way. This will increase Mr. Johnson's estimate of the approaches for a single-track railroad only $33,766. The operation of putting the wagon road on top increases the cost of wagon-road approaches over Mr. Johnson's as estimated by General Rodman $142,462. My arrangement also saves a wagon-road span of 190 feet on the Davenport bank, which amounts to about $17,000. So that the difference in cost, with the wagon road underneath, amounts to $125,696 in favor of the latter plan. This plan is in every way the best, and puts the railroad so high that all the roads leading off the arsenal grounds can pass under it. No one objects to this arrangement, so I presume Congress will not hesitate to direct this change at all events,

With the clear space of 28 feet between the trusses, and the railroad above the wagon road, we make the trusses 33 feet high, so as to give plenty of head room below the top lateral bracing. The railroad floor beams furnish an intermediate system of bracing, so that we can make the vertical posts secure against vibration and buckling. We can make the wagon floor the whole 28 feet wide, put the double track on above it, and then two six-feet sidewalks on the top chord, to be reached by stairs ascending from the ends. This would require for safety a strength of bridge equal to a load of 9,000 pounds per lineal foot of bridge. Or, we can put the sidewalks 5 feet wide inside the truss, leaving an 18 feet wagon way, and then the double-track railroad as before, which would require a strength of bridge equal to a load of 7,800 pounds per lineal foot, or we can have a single-track railroad, with trusses 18 feet apart, giving a wagon road that wide, with two five-feet sidewalks outside the trusses, and this would require a strength of bridge equal to a load of 5,300 pounds per lineal foot.

The cost of these trusses will, on account of the long floor beams in the first two cases, be nearly in proportion to the load they have to carry. It is my design to advertise for proposals to build a superstructure on each plan, and I will have the results ready to present to Congress by the time it meets again. In view of the great load which the bridge will have to carry, if made according to the full requirements of the case, I have confined myself to the least spans allowed by law. It is doubtful whether I could venture to make the draw span any wider, and this being the case, there is no good reason for increasing the others. I have endeavored to keep the requirements of navigation uppermost in locating the axes of the bridge and piers. The position of this axis had been agreed upon between General Rodman and the railroad company before my taking charge, and I found that by locating the pivot pier so as to have one end rest on the island, the axis the of piers would be in the

direction of the current in a place where it maintained a nearly constant direction. The current is, as a whole, nearly at right angles with this axis of the bridge.

In some places it inclines some 3 degrees one way, and some places as much the other. The axis could only be at right angles with the stream by becoming a broken line, and it would have to change its direction with different stages of the river. It was, however, as well situated in these respects as could be expected. Observations with floats show that the eddies below the existing piers affect the course of the floats almost down to the site of the present bridge, but we made enough observations to eliminate the effect, so that we have the main course of the current such as it will be when these piers are removed. We have carefully determined the shape of the bottom of the river, and see that its form does not much affect the course of the current, except near low-water stages.

As before said, the location of the draw near the island placed the pivot pier parallel with the current on the location adopted by General Rodman and the railroad company. This was fortunate, because I had received a petition from the president of both the steamboat companies to put the draw at this place. An examination of the bed showed, too, that by putting it here, the pivot could be placed on 4 feet at low water on the edge of a ledge of rock, whereas by putting it out more in the middle of the stream, the pier would have to stand in 12 feet at low water. The pier placed on the ledge, besides causing less obstruction to the flow of the river, (which obstruction increases the velocity and changes the direction of the current,) would not only cost considerably less in masonry, but also in coffer-damming. For in the case of being next the shore, the coffer-dam can be run out from it, making the island act as one side of the coffer-dam, and this same coffer-dam answers for the abutment. This pivot pier and its protections occupy a space of near 400 feet up and down the river, and I agree with Captain James Ward, president of the Northern Packet Company, that it is, whenever practicable, best to have it next the shore. In passing between it and the island the boats escape all danger of striking the next pier toward which the large size of the pivot pier tends to direct the current. If, too, at any time, it should be desirable to correct the flow of the current past the pivot pier, two short coffer-dams could be run, one from each end of it to the shore, and that space enlarged so as to draw in more water, or contracted so as to shut it out, as the case required.

Every requirement seems to be fulfilled by this position of the pivot pier, except some of those General Rodman regards as important to the arsenal. First, he thinks it will be in the way of the landing for boats which he designed to make in the bay above the bridge. Second, he thinks steamboats will be using the inside space of the draw to drop through, (which is one of the advantages to navigation claimed for the location,) and that thus the seclusion which an arsenal ground should have will be invaded, and trouble be likely to arise between his watchmen and steamboat men, and that it will put the government to the expense of maintaining a watchman at this point. To obviate the first objection, I would suggest making the boat landing at the end of the island below the bridge, which is a very good place for it. As to the second one, I think regulations can be made that will avoid trouble. The expense of working the bridge has to be partly borne by the government, and this will require several men constantly at the draw.

These men could be so armed as to suppress any attempt of vicious men on the steamboats to interfere with the regulations on the island.

I have informed General Rodman of my choice of location. So far as I know I have given his objections, but I do not think them sufficient to change my plan. He has been most friendly and courteous to me in all our dealings, and I am sorry we cannot agree in this matter. I am informed that my arrangements are satisfactory to the railroad company. Having located the draw spans, I make the next span, as the law requires, 250 feet in the clear. The abutment on the Davenport side I place on the line of low water. The curve of the shore is such that there is still water at all medium stages, and I think will not much obstruct the flow of the water, even at the highest floods. The great advantage to me in putting the abutment thus far out is to enable me to get down from the level, ten feet above high water, to the streets of Davenport without too much obstructing them. The city council of Davenport passed an ordinance, at my request, raising the grade of the streets opposite this abutment six feet. This makes a neat plan, with good approaches leading in four directions along the streets of Davenport. From this abutment to the 250-feet clear span next to the draw span, I have divided the space into four spans of 220 feet each in the clear at low water.

The piers are about nine feet thick at the low-water line, so that the lengths of spans, measured from center to center of piers, are four spans, 230 feet each, one span 260 feet, one draw span 366 feet; total of wagonroad bridge is 1,546 feet.

The width of the natural water way of the river at the site of the new bridge is 1,625 feet at the present stage, which is seven and one-half feet above low water, (about half way between high and low water,) and the area of the section is 21,590 square feet. The two abutments will stand nearly at the edge of the still water, and are 1,542 feet apart; they reduce the area of the section by 410 square feet. The section of the piers to stand in the water at present stage is 1,260 square feet, leaving an available water way of 19,920 square feet. The same things at the site of the old bridge are as follows: width of natural water way *1,425 feet; area of natural section at present stage 17,655 square feet. At the island end of the bridge, a point, projecting from the shore above, makes still water about forty feet from the shore, and on the Davenport side, a point and mill pier make still water about one hundred and thirty feet from the shore, both together reducing the practicable width of water way to 1,255 feet, and contracting the water way to 16,265 square feet. The piers in the river, allowing for their oblique position, occupy at least 2,800 square feet of the water way, so that there is left but 13,465 square feet of water way at this time. The mean velocity in the case of the two bridges would be immensely proportional to these practicable areas of section, or about as 1 to 1.48, or nearly as 2 to 3. That is, if the mean velocity at the old bridge were six miles an hour, it would be only four miles per hour at the new bridge. As the water rises, the section at the old bridge widens somewhat on the island side, while the new one will not, but the greater width of the old piers will more than compensate for this difference, and the ratio of the areas of the sections will not be much changed.

I am satisfied there is nothing to be apprehended from too great velocity of the current at my location of the draw spans, for one of the spans will not be in the swiftest part of the current. The highest velocity observed at the site of the new bridge was six feet per second, or four and one-tenth miles per hour. At this time the water was ten

feet above low water. I send a plan and profile of this bridge, but as the reports are generally printed without the diagrams, I have made the description full enough to be comprehended without them.

The contractors have commenced work on the Davenport abutment, and we expect to get two or three piers in this season, but the high water makes it uncertain whether we can do more.

I append letters from Captain W. F. Davidson, president of the Northwestern Union Packet Company, and Captain James Ward, president of the Northern Line Packet Company, urging that the draw be placed next the island.

NORTHWESTERN UNION PACKET COMPANY,

St. Paul, Minnesota, July 24, 1869.

DEAR SIR: Having learned that you have been placed in charge of the construction of the Rock Island bridge, I desire to call your attention to the importance of properly locating the draw.

I trust that from your experience you have seen the necessity that the draw should be so constructed that boats can drop through along the shore, and I have been informed that the bridge is to be so located that the channel will allow such construction. Of course it is not necessary that the draw should be where the boats actually run, but it should be built where the water is of sufficient depth at all times for the boats to pass.

I am gratified that the planning and construction of this bridge has been placed in your hands, feeling, as I do, that your experience will give us a bridge passable at all times, without danger from the wind or dark nights.

Should you desire it, I think I can secure a petition from a large number of prominent practical steamboat and river men to the above effect.

Yours, truly.

WM. F. DAVIDSON, President of the Northwestern Union Packet Company.

General G. K. WARREN, Davenport, Iowa.

ROCK ISLAND, July 30, 1869.

DEAR SIR: Learning that you had charge of the construction of the bridge across the Mississippi River at Rock Island, I beg leave to call your attention to the fact that no bridge across the Mississippi has yet been constructed in accordance with the views of what are called river men, or the people engaged in navigating the Mississippi River. They are almost unanimous in the opinion that one end of the draw should rest on the shore pier, where the water is of proper depth and not subject to change. This would enable boats to land on dark nights and in windy weather, and drop through the draw by means of their lines with safety, and the draw should be as wide as possible.

Yours, very respectfully,

JAMES WARD,

President of the Northern Line Packet Company.

General G. K. WARREN, U. S. A., Davenport, Iowa.

PERSONAL REPORT OF DUTIES OF SELF AND THE DIFFERENT OFFICERS AND ASSISTANTS.

About the middle of October, 1868, I was made a member of a special Pacific railroad commission, to examine and report upon the condition of the Union Pacific railroad, the Union Pacific railroad, eastern division, and the Sioux City and Pacific railroad. This work occupied me continually till the middle of December, and while thus occupied the other works were carried on by my assistants.

The reports on the condition of the above named railroads were made to the Secretary of the Interior. On the 16th of January, 1869, I was made a member of another special commission to re-examine the Union Pacific railroad, and the Central Pacific railroad of California, and determine upon the proper line for uniting them. This duty occupied me until about the 10th of July, 1869. The reports were made to the Secretary of the Interior.

Brevet Major W. H. H. Benyaurd has just reported to me, and will be