SECTION 5.-Accessory works and appendages: Six boats for driving piles, at $1,600 each.. Single-track railroad and accessories. Two locomotives... Sundry buildings, administrator's bouse, lock-tenders' houses, stores, depots, workshop for the machinery, &c. .... $20,000 8,000 9, 600 36, 000 36, 000 30,000 70,000 20,000 35,000 The capital strictly necessary, resulting from what precedes, must therefore be of.... But it would not be prudent, in hydraulic calculations, to place unlimited confidence in an estimate. In order to meet all omissions and unexpected casualties, it is wise to add 1-5 of the total amount, say.... Which brings the total at....... $264, 600 2, 221, 569 444, 313 2, 665, 882 If we look back to the topographical description of the country given by us, it will be remembered that the canal crosses a region of low lands where the sea brings her alluvions, and which she sometimes destroys during her storm. The double dike of the canal, six miles in length, will break the efforts of the sea, and annul its swiftness in that section. The result will be that the lagoons will become real basins of precipitation, the bays will become lagoons, to be filled up in their turn, and the water will recede forever, letting a new continent rise. A few years will be sufficient, even if we consider only the actual rapidity of the increase, to correct permanently and securely to the continent of the left bank of the river this archipelago now filled and leveled. Thereafter a belt levee, similar to that of the canal, is all that will be needed to protect this new soil from the inroads of the Gulf. The river levee protecting it on the other side from the overflows of the Mississippi, we will have conquered from the sea a piece of land of nearly triangular shape, having six miles for the height of the triangle and about fifteen miles at its base, that is to say, a surface of about forty-five square miles. This surface, perfectly plain, formed of argilosilicious alluvions, would probably be suited to all sorts of cultivation, admirably developed by the salted atmosphere, so soon as the soil would have been properly reclaimed from its saline conditions by periodical overflows of fresh water, regulated by means of sluices constructed in the levee of the river. R. MONTAIGU. D. [Maps not printed.] 2. REPORT OF BOARD OF ENGINEERS UPON CAPTAIN HOWELL'S PROJECT FOR A SHIP-CANAL CONNECTING THE MISSISSIPPI RIVER WITH THE GULF OF MEXICO. The board of engineers constituted by Special Orders No. 83, dated Headquarters Corps of Engineers, Washington, D. C., June 30, 1873, to consider and report upon the plan submitted by Capt. C. W. Howell, Corps of Engineers, for a ship-canal to connect the Mississippi River with the Gulf of Mexico, in the navigable waters thereof, made in compliance with a resolution of the House of Representatives, passed March 14, 1871, have the honor to submit this report. The resolution referred to is as follows, viz: Resolved, That the Secretary of War be, and is hereby, requested to cause an examination and survey, with plans and estimates of cost, to be made by an officer of engineers, for a ship-canal to connect the Mississippi River with the Gulf of Mexico, or the navigable wa ters thereof, of suitable location and dimensions for military, naval, and commercial perposes, and that he report upon the feasibility of the same to the House of Representatives. In compliance with the foregoing order the board met in the city of New York on the 25th day of last July, and held a number of meetings during that month, and subsequently thereto, as shown by the minutes of proceedings transmitted herewith. At these several meetings there were examined and discussed not only Captain Howell's project for the Fort Saint Philip ship-canal, as set forth in considerable detail in his report of February, 14, 1873, and the accompanying charts and plans, but descriptions of and reports upon similar works successfully executed by European engineers. It being deemed expedient, before giving a formal expression to their opinions, to visit and examine the site of the proposed canal, as well as to obtain the views of local engineers upon the subject under con sideration, the board adjourned to meet in New Orleans. The board accordingly re-assembled in that city on the 24th day of last November, and on the 25th proceeded down the Mississippi River. viewed the proposed location of the canal, and visited Forts Jackson and Saint Philip, both heavy structures, resting on an alluvial formation in all respects similar to that through and upon which the canal wond have to be constructed. The Southwest Pass was also visited, and the working of the dredge boat at Pass à Loutre witnessed. The opinions of distinguished local engineers were subsequently solicited, and those submitted in writing are attached to this report. The views of prominent citizens of New Orleans interested in the commercial welfare of the Mississippi Valley were also obtained. They are fairly set forth in an article published in the New Orleans Daily Times, hereunto appended. The conclusions formed by the board may be briefly stated as follows viz: 1. From the facts and data presented in official reports and otherwise, from the experience gained on works of the same character, and the many improvements made in the practice of hydraulic engin eering within the last twenty-five years, but, more particularly and per tinently, from the character of the borings made by Captain Howe upon the Fort Saint Philip Peninsula, across which the proposed cana is to run, the board is of the opinion that no extraordinary engineering difficulties in the construction and maintenance of the canal need be apprehended. But it is suggested in order to avoid beds and pockets of quicksand known to exist at some points in this locality, that the precise line of the canal should not be decided upon until a more thorough examination of the sub-strata has been made by borings. It is not improbable that such an examination may indicate the expediency, and perhaps the necessity, not only of adopting a curve, or a series of curves, in preference to a straight line for the axis of the canal, but also of selecting other points of termini than those recommended by Captain Howell. Indeed, one member of the board is in favor of locating the Gulf ter minus to the northward, and consequently under the lee of Sable l'oint, and of securing the requisite depth of water into Isle au Breton Pass by dredging. This would naturally carry the river terminus nearer to Fort Saint Philip, and perhaps within suitable distance from the work to satisfy the requirements of a good defense without the erection of special works for that purpose. The question of affording adequate military protection to the outer end of the canal forcibly suggests the head of Isle au Breton Pass, north of Sable Point, as the proper point of outlet, for the reason that suitable defensive works can be established there at less cost than at any other point. But all those questions are deemed essentially subordinate. They must, of necessity, yield to the paramount consideration of adopting that locality for the canal which shall best secure the requisite stability for the sides and bottom of the prism and the foundations of the locks. 2. With regard to the plan submitted by the engineer in charge, he has stated that it was prepared while pressed with other important duties, and that, under the circumstances, it was not possible to perfect all details of the project, or to make the numerous borings which are considered a necessary preliminary to a precise location of the route of the canal throughout its entire length. The estimate submitted can therefore only be regarded as an approximation to the probable cost of the work. 3. The board approve the débouché of the canal into the Gulf waters of Isle au Breton Pass upon the ground that the advantages possessed by these waters of ample and permanent depth, and good and capacious anchorage grounds, are not only adequate to the objects in view, but are greatly superior to those which obtain in any other locality. A comparison of old charts with those that are more recent, both verified by Captain Howell's survey, shows quite conclusively that the depth of water in this pass, as well as upon the bar at its opening into the Gulf, is quite permanent; and the board coincide with Captain Howell's views that existing circumstances promise a continuance of deep water in this pass. 4. The board also approve the location of the inner end of the canal upon the straight portion of the Mississippi River below Fort Saint Philip, at such distance from that work as the final examination and borings shall indicate as most suitable, due weight being given to the question of providing adequate military protection for the work from existing fortifications, or otherwise, as may be found most advantageous. [For a description of the canal, in order to understand the modifications recommended, reference may be made to Captain Howell's report, and the accompanying plans herewith returned.] 5. Captain Howell's project for the construction of the lift-lock contemplates a coffer-dam surrounding the entire lock. The board entertain doubts of the practicability of this method of construction at a reasonable cost, owing to the nature of the soil and the engineering difficulties consequent thereon. In view of this circumstance, and upon a suggestion made by the senior officer of the board, it is believed the apprehended difficulties may be avoided by replacing the side walls of the lift-lock chamber with gentle slopes of earth, and constructing the upper and lower lockgates, with their foundations and side walls, separate from each other. With these changes the foundations of the ends of the lock can be laid by any one of the several processes well known to engineers. The bottom and sides of the lock-chamber should be riveted as far as necessary. 6. The following modifications of the proposed dimensions of the canal are recommended: Length of lock-chamber increased to 500 feet. Width of lock at the gates reduced to 60 to 65 feet. Depth over sill, at extreme low water in the Gulf of Mexico, reduced to 25 feet. Depth of trunk of canal, at extreme low water in Gulf, (not changed, 27 feet. Width of canal at bottom, (not changed,) 200 feet. Sides of canal to slope about 1 upon 4. A suitable arrangement of sluices must be made to meet these pro posed changes. The foundation and construction of the guard-lock may be the same as for one of the gates of the lift-lock. 7. The jettees, extending the canal into the deep waters of Isle an Breton Pass, will doubtless require more material than the plan sub. mitted by Captain Howell contemplates; but inasmuch as the length of these jettees and their cubic contents depend, to no inconsiderable extent, upon the position selected for them, no very accurate estimate of their cost can be made until the final location is determined upon. 8. It is evident from the foregoing that the necessary and unavoidable absence of sufficient data to determine the best location for the line of the canal across the peninsula, including its termini, and particularly its débouché by jettees into Isle au Breton, renders it impossible to maar a close estimate of its cost. A new estimate, resulting in part from a revision of that made by Captain Howell, has been rendered specially necessary in view of the modifications of plan recommended by the board. It is believed to be ample to cover the cost of constructing a canal of the dimensions given above, located within the limits desiguated. The estimate amounts to $10,273,000. The subject of the improvement of the passes at the mouths of the Mississippi will be separately presented. Respectfully submitted. New York, January 9, 1874. JOHN NEWTON, Lieut. Col. Engineers, Brt. Maj. Gen., U. S. A. Q. A. GILLMORE, Maj. of Engineers, Bet. Maj. Gen., U. S. A. Maj. of Engineers, Brt. Maj. Gen., U. S. A Maj. of Engineers, Brt. Maj. Gen., U. S. A. Captain of Engineers, Brt. Maj., U. S. 3. Not fully concurring, my views will be presented in a separate report. J. G. BARNARD, Col. of Engineers, and Brt. Maj. Gen., U, S. A. 3. NEW YORK, January 20, 1874 GENERAL: Having dissented from the views of the majority of the board of engineers convened by Special Orders, No. 83, June 30, 1873, to consider and report upon the plan submitted by Capt. C. W. Howell, corps of engineers, for a ship canal to connect the Mississippi River with the Gulf of Mexico, I state, at the outset, that, in making separate reports upon the particular "plan" submitted, and upon the alternative of the "improvement of the passes," my object will be to prove 1st. That assuming that a canal is to be made, the plan now submitted suffices only to show that a more protracted and more comprehensive study is required to fix the location and determine the general details of construction, and to make an estimate which can rightly be considered approximate. 20. That before resorting to an artificial work of the difficult and costly character of a "ship-canal," a more attentive consideration of the superior advantages of the natural mouths, and of the fair probability of utilizing them, is needed. Furthermore, I add, that neither difficulties nor costs are to be weighed against the demand for an adequate navigable outlet to the Mississippi River, whether that outlet be a canal or otherwise; but the whether" here becomes, as I think I shall show, the symbol of a question not yet solved in favor of the canal. The first proposer of a ship canal appears to have been Mr. Benjamin Buisson, who, in 1832, suggested that a canal "six and a half miles long, commencing on the left bank of the river, a few miles below Fort Saint Philip, and entering the sea about four miles south of Breton Island, would afford an easy and safe access to the river to vessels drawing 20 feet." Subsequently, Lieut. B. Poole, a graduate of the Military Academy, serving as topographical engineer, surveyed (or, more accurately speaking, reconnoitered) this route, and reports (1837) that a canal here"offers a fairer prospect of opening the Mississippi to ships of the largest class than any other plan that has been spoken of." But it remained for the late Major W. H. Chase, of the Corps of Engineers, to give the canal project a defined form by projecting in an official report dated February 9, 1837, what may be (though without drawings) properly styled a plan for "a ship-canal to connect the Mississippi River with the Gulf of Mexico." This plan is best exhibited by an extract from his report. He says: The obstacles presented to an easy entrance of the Mississippi by vessels drawing 12 feet of water, are productive of great injury to the commerce of New Orleans, and require to be promptly removed, or, failing to be done, the construction of a ship-canal on the plan Indicated by Major Buisson, should be resorted to. By reference to chart, the line of the proposed canal is exhibited, commencing at a point About two and a half miles below Fort Jackson, and extending seven miles to the shores of the Gulf, and thence, by a jettee 1,760 yards, to 30 feet water. It is proposed to carry into effect this plan of a ship-canal I. By a construction of a guard-lock at the junction of the canal with the river. The object is to prevent the flowing of the river into the canal. II. The excavation of the trunk of the canal, 100 feet wide at top, 30 feet wide at bottoin, and 30 feet deep. The object of such large dimensions is at once to provide not only For the entrance of the largest ships engaged in commerce, but also of ships of war of the rgest class. The advantages offering for both classes of vessels are obvious, and need no Comment. III. The construction of the jettees or breakwaters of large dimensions, having for their ase 100 feet, with a depth varying from 5 to 30 feet, and 20 feet wide at top, and raised to the level of high water. H. Ex. 113—5 |