built with an unbroken or continuous span of not less than 400 feet in the clear from pier to pier; in all other respects in accordance with conditions, &c., of an act to establish certain post-roads, approved July 14, 1862.

Joint resolution approved April 7, 1869, authorizes the building of a bridge at

PADUCAH, KY., with a continuous span of not less than 400 feet in the clear; in other respects, in accordance with act approved July 14, 1862.

Act approved July 11, 1870, directed the Secretary of War to detail three engineers to examine all bridges now erected or in process of construction across the Ohio River, and to report whether such bridges will interfere with the free and safe navigation of the river, and, if they do, to report what extent of span and elevation above water will be required to prevent such obstruction, and an estimate of cost to change them.

Act approved July 14, 1870, amending act approved July 20, 1868, allowing the bridge at

SAINT JOSEPH, Mo., to be built on the terms and subject to limitations of the act of Congress approved July 25, 1866, provided if built as a draw-bridge the spans of the draw shall not be less than 200 feet in the clear on each side of the central point.

Act approved March 3, 1871, made it unlawful to proceed in the construction of the bridge over the Ohio River from—

CINCINNATI, OHIO, TO NEWPORT, KY., now being constructed, unless so constructed that the channel-span of 400 feet, as located, shall have a clear headway at low water of 100 feet below any point of the span. In such case no draw would be required. Further required that proposed changes by the company should be submitted to the Secretary of War for his approval. It also provided that the company could, after making the changes, file a bill in equity in the United States circuit court, and gave the courts jurisdiction.

Act approved February 24, 1871, authorized the construction of a railway and highway bridge over the Missouri River at

OMAHA, NEBR., under the provisions of the act approved July 25, 1866, authorizing the bridge at Quincy, &c., provided that if constructed as a draw-bridge it shall have draw-spans of not less than 200 feet in the clear on each side of the pivot-pier.

Act approved March 3, 1871, authorized the bridging of the Mississippi River at

LOUISIANA, Mo., and provided that if built with unbroken and continuous spans it should not be of a less elevation than 50 feet above high water mark to the lower chord of the bridge, nor should the spans over the main channel be less than 350 feet in length, and provided that if built as a draw-bridge the draw should be over the main channel with spans not less than 200 feet in length in the clear.

Section 6 authorized the construction of a bridge over the Missouri River within 9 miles of

GLASGOW, MO., provided that the said bridge shall be made with unbroken and continuous spans of the same height and lengths as provided for a high bridge at Louisiana, Mo.

Act approved March 3, 1871, appropriated $500,000 for completing the ROCK ISLAND BRIDGE; it being an unexpended balance covered into the Treasury.

Act approved March 5, 1872, authorized the building of a railway and highway bridge by the "Saint Joseph Bridge Building Company" at

SAINT JOSEPH, Mo., either as a high bridge or low draw-bridge; if high not less than 50 feet above extreme high water mark.

Nor shall the spans of said bridges be less than 350 feet in length, and the main span shall be over the main channel of the river and not less than 300 feet in length.

If built as a draw-bridge, the provisions are the same as in the act approved July 25, 1866, authorizing the bridge at Quiney, &c. This act provides that a plan of the bridge must be submitted to the Secretary of War for his approval. The company shall not assign the charter which it now holds by assignment from the Saint Joseph and Denver City Railroad Company, nor construct any other bridge.

Act approved April 1, 1872, authorized the building of a bridge over the Mississippi River within 15 miles of

CLINTON, IOWA, not to interfere in any manner with approaches or piers of the bridge now constructed at Clinton, under the limitations as to dimensions of spans as provided in the act approved July 25, 1866. All railroad companies desiring to use it shall be entitled to equal rights in the passage of it, upon terms and conditions prescribed by the Secretary of War.

Section 5 provides that the Secretary of War shall have power to make regulations for the security of navigation, and the bridge shall be changed at the expense of the owner.

Section 6 authorizes a bridge at

MUSCATINE, IOWA.

Section 7 authorizes a bridge at any point between the counties of— WHITESIDES AND CARROLL, ILLINOIS, and JACKSON AND CLINTON,

IOWA.

Section 8 authorizes a bridge to be built at—

LA CROSSE, WIS., by the Milwaukee and Saint Paul Railroad Company.

Act approved May 1, 1872, amends act approved March 5, 1872, but did not change any of the required lengths and heights of span. Act approved May 11, 1872, authorized a bridge at

BOONVILLE, Mo., to be built under the requirements of act approved July 25, 1866.

at

Act approved May 15, 1872, authorized a bridge over Lake Saint Croix

HUDSON, WIS.; draw to be 320 feet long over all, with two spans of 140 feet in the clear, for the passage of boats; one span, 136 feet in the clear, for the passage of rafts. No provision was made as to height.

Act approved May 17, 1872, authorizes a railway and highway bridge

to be built at

QUINCY, ILL., under the same provisions as in act approved April 1, 1872, for a bridge at or near Clinton.

Section 7 authorizes a bridge at

WARSAW, ILL. A provision of the act was that this bridge be commenced within eighteen months.

Act approved May 25, 1872, authorizes a bridge at

FORT MADISON, IOWA, under the provisions contained in act approved April 1, 1872, for a bridge at Clinton, &c.

Act approved June 4, 1872.—All bridges hereafter constructed over the Mississippi River, under authority of any act of Congress, shall be subject to all the terms, restrictions, and requirements as to length and height of spans, &c., of the act authorizing the bridge at or near Clinton, Iowa, approved April 1, 1872.

Act approved June 4, 1872, authorizes the Davenport and Saint Paul Railroad Company to pass their cars over the bridge at Rock Island, under certain provisions.

Act approved June 4, 1872, authorizes the building of a railway and highway bridge at

NEBRASKA CITY, NEBR., under the provisions of act approved July 25, 1866. Section 2 provides that the charter shall be for the use and benefit of any person or corporation who shall complete the bridge, and that the said corporators may be compelled to make the transfer of the charter by any court having jurisdiction.

Provided, That the said Nebraska Bridge Company and their associates shall fail to commence in good faith the erection of said bridge within one year from the passage of this act and complete the said bridge without unnecessary and unreasonable delay in accordance with the provisions of this charter.

Act approved June 4, 1872, authorizes building a railway bridge across the Missouri River at

BROWNVILLE, NEBR. If high, 50 feet above high water; spans, 250 feet; main span, 300 feet; if a draw-bridge, draw-openings not less than 200 feet; adjoining spans, 250 feet; 10 feet above high-water.

Act approved June 10, 1872, authorizes a railway bridge to be built at or near the city of

RED WING, MINN., under the provisions of act of July 25, 1866.

Act approved December 17, 1872, authorizes the bridging of the Ohio River, for railroad or other purposes, by any one having authority therefor, upon compliance with the provisions and requirements of this act. Every bridge above the mouth of the Big Sandy shall have at least one span of a height of not less than 90 feet above low water and of not less than 40 feet above local high water; that this high span shall give a clear opening of at least 400 feet between the piers, and shall be placed over the main channel. If the high span is not over the low water channel, suitable arrangements to be made elsewhere to permit the pas sage of single boats at low water. All bridges over the Ohio below the Covington and Cincinnati suspension bridge shall have in addition to the high span prescribed above a pivot-draw with two clear openings of 160 feet each. If the conditions of this act cannot be complied with the Secretary of War shall appoint a board of three experienced officers of the Corps of Engineers to examine the case, and may on that recommendation authorize such modifications in the requirements of this act as will permit the construction of the bridge. All bridges over the Ohio shall maintain such lights as may be required by the Light-House Board. This act authorized the building of one bridge at

WHEELING, W. VA., with a span over the main channel of not less. than 350 feet in length.

Joint resolution number ten, approved April 7, 1869, authorizing a bridge at

PADUCAH, KY., was repealed by this act.

Standard steam-pressure for tow and freight boats on the Mississippi River and tributaries changed from 110 to 150 pounds by this act.

Act approved March 3, 1873, authorizes the Saint Clair and Carondelet Bridge Company to bridge the Mississippi from the southern part of— SAINT LOUIS.-The bridge must have two spans over the main chan nel of not less than 500 feet in the clear at low water mark, no span over the water at low water mark to be less than 250 feet in the clear. The elevation of the bridge over the main channel shall not be less than 100 feet above low water mark, measuring to the lowest part of the superstructure, or in case of arch spans, to the lowest point of the center of

the arch; that it shall have two railway-tracks, two highway-tracks, and two foot-walks of not less than 8 feet in width.

Act approved March 3, 1873, authorizes a railway-bridge over the Missouri River at

LEXINGTON, Mo., to be built under the same provisions as contained in act approved July 25, 1866.

Act approved June 6, 1874, legalized the railway and ponton bridge across the Mississippi River at

PRAIRIE DU CHIEN, WIS.-Section 4 of this act provides that the bridge authorized at or near

CLINTON, IOWA, by act approved April 1, 1872, may be constructed as a pile and ponton bridge, with a draw not less than 408 feet in width. Act approved June 22, 1874, authorized the Milwaukee and Saint Paul Railway Company to construct a bridge at a point heretofore selected atLA CROSSE, WIS.; a board of engineers to be convened to report what accessory works are necessary to secure a straight channel-way for navigation; the board to determine the location of piers and height of bridge; company not to proceed with the building until report of the board is approved by the Secretary of War; superstructure not to be commenced until accessory works are constructed; a provision that the said company shall not charge more than $3 a car for each freight-car transported across said bridge.

Act approved June 23, 1874, appropriated $23,400 for

ROCK ISLAND BRIDGE, for alterations and repairs and additional machinery (for draw of bridge), and for care and preservation, one-half of which sum to be reimbursed by the Chicago, Rock Island and Pacific Railroad Company.

Act approved March 3, 1875, act amendatory of the act approved March 3, 1873, authorizing bridge over the Mississippi at

SAINT LOUIS, Mo., allows two straight continuous spans of not less than 450 feet in the clear. Section 2 requires the company to close Cahokia Bend if the site on plan numbered "2" submitted to the Secretary of War be accepted.

Act approved March 3, 1873, authorized a ponton wagon-bridge across the Mississippi River at

DUBUQUE, IOWA, subject to all the terms, &c., of act legalizing a ponton railway-bridge at Prairie du Chien, Wis., approved June 6, 1874, subject to the provision that it shall have a draw 500 feet wide and that plan and location shall be subject to the approval of the Secretary of War.

Act approved July 6, 1876, authorizes the city of

LA CROSSE, WIS., to construct a pile and ponton bridge across the Mississippi River, subject to all the terms of act legalizing the Prairie du Chien railway ponton bridge approved June 6, 1874, with the modifi. cations that it shall have one draw of not less than 400 feet, and that plans and location must first be submitted to the Secretary of War for his approval.

Act approved July 8, 1876, authorizes the Nebraska City Bridge Company to build a ponton railway-transit and wagon bridge across the Missouri River at

NEBRASKA CITY, NEBR., with a draw 300 feet wide; design and drawings of the bridge and a map of the location for one mile above and one mile below the bridge shall be submitted to the Secretary of War for his approval before the bridge shall be built.

Act approved August 15, 1876, authorizes the Sioux City Bridge Company to build a railway and highway bridge over the Missouri River at

SIOUX CITY, Iowa.-It may be built as a high bridge 50 feet above extreme high water, all spans 300 feet; or as a draw-bridge, same dimensions, &c., as act approved July 26, 1866. If the company elect, the Secretary of War may authorize the building of a pile or ponton bridge subject to the restrictions in the act legalizing the Prairie du Chien bridge, approved June 6, 1874, except that it shall have one draw 400 feet wide in the clear; plans of bridge and location to be subject to the approval of the Secretary of War.

CHAPTER VI.

GENERAL ACCOUNT OF THE WAY THE SURVEYS AND INVESTIGATIONS HAVE BEEN MADE.

Description of surveys made in 1866, '67, '68, '69, and '76—Circumstances under which the maps and report were prepared-LIST AND DESCRIPTION OF ORIGINAL MAPSCOMPILED MAPS ON A SCALE OF TWO INCHES TO A MILE-Map on scale of an inch to six miles-LIST OF MAPS COLLECTED AND USED IN THE COMPILATION.

Surveys in 1866.-This description of surveys includes not only those made at bridge sites, but such as were made for the purpose of improv. ing places of difficult navigation, more particularly of the river between the Falls of Saint Anthony and Rock Island. The subject of improvement will be treated in a separate report, but the surveys are all described here, as they were really included in the requirement of the bridge investigation "to survey the whole river." The same parties did the field-work for both purposes. Mr. J. P. Cotton, civil engineer, was from the first employed on this work, and for much the larger portion of the time he was in charge of these surveys. He has, also, with other assistants, under my direction, prepared all the maps and other drawings, and aided me in every part of this work.

The short time remaining between my arrival in Saint Paul, in August, 1866, and the close of the season, coupled with the fact that my report upon these surveys had to be submitted to Congress at its next session, in December, precluded the possibility of making a continuous survey of more than a small portion of the river upon which I was to report. I therefore concluded to make a reconnaissance of the whole river from Saint Anthony to Saint Louis, and to make detailed surveys at points where navigation was obstructed, and at bridges, and at proposed and probable sites of bridges.

For this reconnaissance, the steamer G. B. Knapp was chartered at $1,000 per month. She was a new steamer, built to run between Stillwater, Minn., on Lake Saint Croix, and Saint Paul, Minn. Her draught, when light, was only about 20 inches. The light draught enabled her to run in any channel that could be navigated by freight ing steamboats. The boat was in charge of a captain, a pilot, two engineers, fireman, and deck-hands. Difficulty, as usual, was found in organizing a party to make the instrumental surveys. This was the first work in that section of the country requiring engineers possessed of practical knowledge in river surveying, and want of time prevented bringing them from other places.

Mr. C. C. Smith, an engineer of ability, whom I employed, succeeded in getting together the following party, viz: T. P. Gere, J. P. Cotton, A. D. McSweeny, C. H. Conwell, and H. D. Van Pelt. These men had come to this part of the country for various reasons, and had been en