mode of towing and sailing and the kind of vessels are so widely different, that I will not occupy your time with any further remarks, as I believe you are perfectly familiar with both. I will not take up any time on the question of the great loss said to be sustained by the railroads, caused by the ice blocking the river during a part the winter, for, I believe, you will have facts enough brought before you to show that such a loss is only in the imagination, and not in fact. For many years the people of the Northwest, and of Michigan in particular, have been asking Congress for large appropriations of money to improve our harbors and remove obstructions from our rivers, and they never could get enough, and now we have a few asking Congress to place obstructions across our rivers to spoil the natural outlet for the products of the great Northwest, and, as a consequence, increase the cost of transportation; for, when you stop navigation, up goes the freight by rail. In conclusion, gentlemen, permit me to ask you to consider well this subject before you recommend that permission be granted for a bridge, for I believe such would be a very serious and costly obstruction to the safe navigation of our rivers. Very respectfully, yours, DETROIT, November 20, 1873. JOSEPH NICHOLSON. Capt. J. Nicholson has been an able and respected sailing-captain and insuranceagent. I am well acquainted with him, and have full confidence in his judgment and views on any subject pertaining to the navigation of the lakes. E. B. WARD. Q3. ST. LOUIS AND ILLINOIS BRIDGE ACROSS THE MISSISSIPPI RIVER. Letters of the Chief of Engineers. OFFICE OF THE CHIEF OF ENGINEERS, Washington, D. C., March 26, 1874. SIR: I had the honor October 6, 1873, of submitting to you the report, dated September 11, 1873, of a Board of Engineers convened at St. Louis, Mo., by Special Orders, No. 169, War Department, AdjutantGeneral's Office, dated August 20, 1873, "to examine the construction of the St. Louis and Illinois bridge across the Mississippi River at St. Louis, and report whether the bridge will prove a serious obstruction to the navigation of said river, and if so, in what manner its construction can be modified." A copy of the report was furnished to the bridge company. The Board was reconvened on January 14, and on January 31 a supplementary report was submitted by it. I now have the honor to transmit copies of the two reports of the Board, and, concurring in their views respecting the obstruction to navigation which the peculiar construction of the bridge forms, to renew my recommendation that the subject be submitted to Congress. Very respectfully, your obedient servant, Hon. W. W. BELKNAP, A. A. HUMPHREYS, Brig. Gen. and Chief of Engineers Secretary of War. OFFICE OF THE CHIEF OF ENGINEERS, Congress, by acts approved July 25, 1866, and July 20, 1868, (Statutes at Large, vol. 14, pp. 245, 246; vol. 15, p. 123,) authorized the St. Louis and Illinois Bridge Company to build a bridge across the Mississippi River at St. Louis, Mo. This bridge is now in process of construction, and, representations having been made, by parties interested in preserving the free navigation of the river, that the bridge, when completed, would materially obstruct and injuriously modify that navigation, a Board of officers of engineers was ordered to convene at St. Louis, and, after a careful examination of the whole subject, to "report whether the bridge will prove a serious obstruction to the navigation of said river, and if so, in what manner its construction can be modified." The Board met in accordance with the order, and in pursuance of their instructions made a report, which is herewith respectfully submitted. The Board confined itself strictly to the consideration of the question whether the bridge will prove to be a serious obstruction to the navigation of the Mississippi River, and if so, to the remedy therefor. Having obtained from the representatives of the navigation interests on the one hand, and from the officers of the bridge company on the other, the statistics and drawings necessary to a clear comprehension of the subject, and having caused examinations and measurements to be made under their own direction to assure the accuracy of the latter, the Board are unanimously of the opinion "that the bridge, as at present designed, will prove a very serious obstruction to the free navigation of the Mississippi River." The Board, in addition, state that arched trusses like those in the bridge under consideration "present so many difficulties to free navigation, that in future their use should be prohibited in plans for bridges over navigable streams." No satisfactory plan for changing the present structure could be decided upon; and as it was deemed "absolutely necessary that some provision should be made for allowing large boats to pass the bridge with safety," when necessary, the Board recommend "as the most feasible modification a plan which has been already tried and found efficient at the railroad bridge over the Ohio River at Louisville, Ky.," viz: "A canal, or rather an open cut, be formed behind the east abutment of the bridge, giving at the abutment a clear width of water-way of 120 feet." The shore side of this cut to be laid out on an easy curve joining the general shore-line about 500 feet above the bridge, and about 300 feet below it. This opening to be spanned by a draw-bridge, giving a clear span of 120 feet in width. This plan would enable boats of the largest class to pass the bridge in any weather, and at any stage of water, with but little delay. The steamboat interest would, it is stated, be satisfied with this modification, and the bridge company object to it only on account of the delay to railroad trains caused by the opening and closing of the draw. Detailed estimates of the cost of this modification can only be given after a special survey and study of the locality. The modification proposed by the Board will not interrupt the work of constructing the bridge. The views and recommendations of the Board are concurred in by me, and it is recommended that the matter be submitted to Congress at its next session for such action as in their judgment may seem to be neces sary. It is further suggested that the Chief of Engineers be authorized to furnish the bridge company with a copy of this communication and the report of the Board Very respectfully, your obedient servant, Hon. W. W. BELKNAP, Secretary of War. A. A. HUMPHREYS, Brig. Gen. and Chief of Engineers. The recommendations of the Chief of Engineers are approved by the Secretary of War, October 10, 1873. Report of the Board of Engineers. ENGINEER OFFICE, UNITED STATES ARMY, St. Louis, Mo., September 12, 1873. GENERAL: I have the honor to transmit herewith, for your consideration, the report of the Board of engineer officers convened by Special Orders No. 169, War Department, Adjutant-General's Office, Washington, August 20, 1873, to examine and report on the Illinois and St. Louis bridge. The papers furnished for the information of the Board are herewith returned. I am, general, very respectfully, your obedient servant, Brig. Gen. A. A. HUMPHREYS, ENGINEER OFFICE, UNITED STATES ARMY, St. Louis, Mo., September 11, 1873. GENERAL: The Board of engineer officers convened by Special Orders No. 169, War Department, Adjutant-General's Office, Washington, August 20, 1873, "to examine the construction of the St. Louis and Illinois bridge across the Mississippi River at St. Louis, and report whether the bridge will prove a serious obstruction to the navigation of said river; and if so, in what manner its construction can be modified,” have the honor to submit the following report: In considering the subject laid before them, the Board have confined themselves strictly to their instructions, which direct them to ascertain whether the bridge, as being built, will be a serious obstruction to the navigation of the Mississippi River; and if so, what modifications can be made in its construction. They have not undertaken to decide whether the bridge is, or is not, being built in conformity to the acts of Congress authorizing its construction, although this question will be of importance when it becomes necessary to decide who shall pay for such modifications as may be determined on. The Board have obtained from the steamboat-men who complain of the present structure a statement of their objections and the reasons therefor. They have obtained from the officers of the bridge company such drawings and statistics as were needed for a clear comprehension of the nature of the structure, and have caused a sufficient number of meas urements to be taken to assure them that the drawings herewith submitted are substantially correct. Appended to this report are the following documents and drawings: A. Copy of special order convening the Board. B and C. Copies of acts of Congress authorizing the construction of the bridge. D. Tracing giving profile of bridge and approaches, (furnished by the bridge company.) E. Tracing showing elevation of center and west spans of bridge, and portion of western approach, (furnished by the bridge company.) F. Tracing showing the outline of the lower part of the superstructure as originally designed, and as now being constructed, (furnished by the bridge company.) G. Water-record of the port of St. Louis for the last thirteen years giving the duration of various stages for each mouth of each year, and also some special observations, taken previous to the continuous records. (Compiled by the board from the official records.) H. Tabular recapitulation of the above, giving the duration of various stages for each year, the average yearly duration of each stage, with the corresponding heights under the center of the middle span, and the heights available for a width of 174 feet, or 87 feet on each side of the center of the arch. I. Drawing showing outline of center arch, with lines of extreme high and low water, and also the width of clear headway available at different heights above extreme lowwater. (Prepared by the Board.) K. Tabular statement giving the most important dimensions of some of the principal steamboats plying to and from the port of St. Louis. (Furnished by the Boatmen's Association of St. Louis.) L. Diagram giving graphically the heights of chimneys and pilot-houses of steamboats enumerated in the preceding list, and showing the relative height of the chord of center arch, which is 174 feet long and 5 feet below the crown of the arch, for different stages from extreme low-water of 1863 to extreme high-water of 1844. (Prepared by the Board.) These drawings, &c., present the general features of the structure so clearly that a detailed description seems unnecessary. The objections made to the bridge are as follows, viz: 1st. The height under the lower arch is so small that a large proportion of the boats which will have occasion to pass under it must lower their smoke-stacks at all, or nearly all, stages of the river, while many of the larger boats will not be able to pass under it during the higher stages, even with their smoke-stacks down. 2d. The small height afforded is only available for a portion of the whole span, owing to the arch-form of the lower part of the superstructure. Moreover, the difficulty of passing under the exact center of the arch will be very great, especially in foggy or windy weather, and any considerable deviation to either side may bring the boat's upper works in contact with the bridge. 3d. These difficulties would probably deter most boats from ever passing the bridge, thereby preventing the ready transfer of freight from one boat to another, or its delivery and shipment at different parts of the city, without resorting to costly transfers by drays or barges. This, it is claimed, would practically cut the Mississippi River in two at this place. An examination of Appendixes K and L will show that the first point is well sustained. The list of boats enumerated therein comprises only those which happened to be in port at the time the Board was in session, or whose dimensions were attainable. It might have been increased considerably had time been available. The apparently unreasonable height and size of the chimneys in general use on these steamboats, are really essential to secure a good draught to the furnaces and economical combustion of fuel. Artificial means to produce the same end are generally very expensive, and often ineffective. Although it is a comparatively easy task to lower small chimneys, dealing with those of large size is a very serious matter indeed. Their weight is so utterly disproportionate to their strength, even when new, that no machinery yet devised will enable large chimneys to be lowered either wholly or in part, without very great labor and danger. The elevated position of the pilot-house is necessary to enable the pilot to have an unobstructed view of the river ahead and astern of his boat. Experience has decided this point most clearly. The second objection is mainly owing to the peculiar system of superstructure employed, and which we understand was adopted principally on the ground of economy. Appendix I gives the widths which are available under the center span at different heights above extreme lowwater. The side spans have not been considered, as they are four feet lower than the central one. Appendix F shows the lower line of the superstructure as originally designed, with the railroad-tracks below the arch for a portion of the width (226 feet.) By a subsequent modification, the lower arched tube was lowered 4 feet at the crown, while the railroad-tracks were raised through a similar distance. This brings the roadway entirely above the arch and increases the height at the center of the arch about 4 feet. The practical conditions are, however, but little altered by this modification. The full height is only given at the exact center of the arch, and in order to consider the matter in its practical bearing, it is necessary to assume that some definite width will be required for the safe passage of a boat. The width of draw spans required by congressional legislation up to this date varies from 160 to 200 feet. The former width would be too small for the large boats used on the Lower Mississippi, and an approximation to the greater width would probably be necessary. The horizontal chord of the center span, which lies 5 feet below the crown of the arch, is 174 feet long, and gives the least width of water-way which seems compatible with safe navigation. The height of this chord is 50 feet above the city directrix. It may therefore be assumed that a boat no portion of whose structure extended above this limiting height, might pass safely under the bridge, provided that the pilot was enabled to keep her within the space mentioned, viz, 87 feet on each side of the center of the span. The position of this chord with reference to different stages of water is given in Appendix L, which also shows the relative height of the chimneys and pilot-houses of a large number of the boats which will wish to pass under the bridge when it is completed. There remains still to be considered the practical difficulty of keeping a boat within the limited width necessary for safety. It is the opinion of the Board that this will be a matter of very great uncertainty, and this is also the view taken by intelligent pilots who were questioned on this point. They maintain that the same width of water-way between piers with clear headway above, would be far preferable. The reason given for this is that the piers would define the available width with exactness; they are easily seen and can be avoided. In case of wind a boat can be dropped through the opening by lines. made fast to ring-bolts on the pier itself.* In case of striking them under headway the damage done is to the hull alone, and, even if so great as eventually to sink the boat, time will generally he afforded to save the lives of the crew and passengers. In the case of a wide arch, however, the case is different. The piers are too far apart to be of service as guides, and lights placed on the structure will be so nearly overhead as to be of no great assistance. If range-lights could be placed at some distance above and below the bridge *In this case the piers would have to be extended up stream about 400 feet by cribs, piles, or other suitable means. |