reduction in the 24 feet depth originally given to the canal. Then, again, the cause would exist either in a bar formed at the entrance of the canal in the sea, or in alluvions deposited by the waters of the river. As regards the sea, we have seen that the canal opens on the west pass of Breton Island, at a point where the waters of the Gulf becoming compressed increase in speed, and rather tend to deepen their bed instead of filling it. This circumstance is sufficient to prove that the sea, instead of forming a bar at the entrance of the canal, would, if a foreign agency created one there, take it crosswise and sweep it off. Can we feel as secure on the river-side? The waters as they enter the lock bring at each sluice-full a volume of 14,400 cubic feet, representing about 85 cubic feet of earth. It is apparent that with twelve sluice-fulls per day, the progressive filling up of the canal might be feared, but a very simple disposition, sanctioned by experience, enables us to avoid this inconvenience. A gate made in the center of the laterals forms the opening to a vault which crosses the thickness of this mason-work and opens on a discharging canal. The sill of this door or gate is on a level with the water-line of the canal, and it is closed when the waters of the river enter the lock. So soon as the level is established between the lock and the river, and when the ships have passed from the river into the lock, instead of opening the gates of the middle sluice, this lateral gate is opened; the river-water, which, from its lesser density, has in great part floated upon the salt water, runs out by this outlet, and the gates of the middle sluice are only opened when the level has come down to the water-line. By this means the waters of the river only penetrate into the channel in very trifling quantity. Besides, if any accretions were formed in the channel or in the locks on the riverside, it would be sufficient to take advantage of the season when the river being at a low-water mark and the sea at high-water, (the level of the latter is a few feet higher than the former,) to use this difference of level for sweeping off of all deposits that might have accrued. As to the accretions we might suppose would exist in the river at the entrance of the head sluice, the study of the river's course has proved that, from its natural regimen, they are not to be feared, the accretions forming themselves on the opposite bank. Thus, all the objections that might be raised against the opening of an artificial outlet to the Mississippi have been met. The circumstances in which we execute it must free us forever of all fear that those two great obstructors of the passes, the Mississippi and the sea, could inspire. EXPENSES AND REVENUES OF THE CANAL. The estimation of the cost of the canal and its revenues is subdivided in several chapters, which may be recapitulated under the following titles: 1. Value and supply of the materials. 2. Order and direction of the works. 3. Value of the works. 4. Means of execution. 5. Revenues of the canal. 1.- Value and supply of the materials. The necessary materials are wood, granite, iron, cast iron, brick, lime, sand, pozzolana, shells, and fuel. Examining, according to the rules of engineering, the resources presented by the locality, we must be surprised to find so many assembled on this spot. Excepting granite and iron, we find all the other materials on the spot and in a very limited space. WOOD.-It is well known that the coasts of the Mississippi are one of the greatest markets for pine and cypress lumber. For more than half a century France and England have been receiving cargoes of lumber shipped from Ship Island and Pensacola. Now these two points are only distant, one sixty miles and the other one hundred and twenty miles from the canal. All the pine and cypress needed will, therefore, reach us by a direct line of navigation. The pine logs for the piles will come at $5 per thousand feet, delivered; the same sold as worked timber will not cost over $10 per thousand feet; two-inch pine boards will be worth $11. The cypress timber will come at $25; the cross-ties for the railroad will cost 75 cents apiece. Oak timber brought from St. Louis, by the way of the river, may be calculated at $35. IRON AND CASTINGS.-Iron will only be used for smith's work, and to strengthen joints. It is an important matter in our calculations. It may be valued at 7 cents per pound, and nails at 4 cents-all delivered. The cast iron will be used principally for the railroad, and will cost $35 per thousand pounds. GRANITE. The granite will be shipped from Boston, bored to order; it will cost $1.25 per cubic foot. BRICKS.-No better earth for the manufacture of bricks can be found than that coming from the excavations of the canal itself. They will be made on the spot at a cost of $7 per thousand. LIME. We have mentioned an island near Fort St. Philip, called "L'ile à Coquilles," (Shell Island.) It is a large shell mound, furnishing all the necessary material for the manufacture of lime on a large scale. This line can be made at a cost of 75 cents per barrel. POZZOLANA.-The marly clay of which we have spoken will furnish the artificial pozzolana intended to change the common shell-lime into hydraulic lime. It may be valued at 50 cents. SANDS, SHELLS, CLAY.-These materials, which are to be found on the spot, have no other value than that of the necessary labor to gather them. We will set them at 10 cents per barrel. FUEL. The only cost of fuel will be the labor and transportation from the banks of the river to the spot where it will be used. The inexhaustible quantity of drift-wood on the river furnishes logs, which the inhabitants on that coast have split, and sell as cord-wood to the steamboats. This wood may be valued at $2 per cord. Order and direction of the work. In order that the following estimate may be understood without an examination of the detailed plan of the canal, it is proper to indicate how the works will be organized and how conducted, so as to be completed in the space of two years. The lines of axis and outlines being marked on the ground, a gang of ditchers will dig up all the cube of earth on the bank of the river that exceeds the level of its waters. Then, two dredging-machines of 35 horse-power, and capable of excavating the depth of 12 feet, will commence at the bank of the river; they will clear all that space to be occupied by the lock and its sluices, leaving to the sides of this lump the necessary talus to prevent the caving in. This lump once cleared, one of the machines will dig on the axis of the canal a passage of 50 feet, and, after following the passage for a distance of 200 feet, it will place itself crosswise and will begin the excavation of the channel on one of its banks. The other machine, passing by the same road, will turn in the opposite direction from the first, and will commence with the channel on its other bank. They will continue this operation indefinitely. Behind them a dredge-boat of 50 horse-power will proceed to the final excavation, to the total depth of 24 feet. During this time three pile-driving boats will begin driving the necessary piles for the formation of a dike in the river, intended to inclose in front the space of the lock. Another of these boats will drive the piles of the dike at the end of the space where the dredge-boats will have entered the channel. When the dikes will have been completed, a draining-machine of 30 horse-power will empty completely the space and maintain it perfectly dry. Then will begin the driving of the piles for the construction of the first floor. A trellis-work will be placed on these piles and the hollows filled with béton. The trellis will be covered with a floor, on both sides of which will begin the lateral walls of the lock. A second trelliswork, with a band under each counterfort, will extend the whole length of the lock between the lateral walls, and will receive the double flooring of frame. The mason-work of the lateral walls will be 34 feet high, 12 feet thick at the top and 24 at the base. It will be buttressed on the land-side by 22 counterforts of Same thickness. The outside facings of the lateral walls will be of granite, the interior masonry of bricks laid in hydraulic cement. While, on the river-side, the excavating of the channel and the construction of the lock will be carried on, the same operation will be performed on the sea-side. A dredge of 50 horse-power, with capacity to excavate 24 feet, will begin the excavation from the deep-sea side, going toward Pavillon Island, on a line with the axis of the canal. When it will have excavated the space to be occupied by the mole and by the two heads of the pier, two pile-driving boats will come and drive the piles, by means of which will be constructed two dikes, one for the head of the north pier, the other for the head of the south pier with the mole attached. When it will have reached a 12-foot depth, the 50-foot horse-power dredge will be replaced by another of 35 horse-power, which will continue the channel between the two piers of the necessary width not only for the channels, but also for the foundations of the piers; it will work this way as far as Pavillon Island. Then begins the same kind of work as at the river-head, to wit, excavating of the lump for the sea-side sluice, lengthening of a passage 50 feet, to introduce the dredge-boat in the line of the channel, the excavation of which will be done by this boat until it will have met the two other boats coming from the river-end. Meanwhile, two dikes, one on the sea, the other in the 50-foot passage, will inclose the lump intended to receive the sluice on the sea-side. When it will have completely inclosed, the draining-machine will drain it, and the pile-driving, trellis-frame, béton-filling, laying of the flooring and frame-work, will be constructed in the manner already explained. The masonry will be made in the same style and proportions, with granite facings, like all the other exterior facings of the constructions of the canal. The piers and mole will have been constructed in the mean time, and these works are carried on simultaneously. The mole is a pile of brick-work (it could be constructed of béton) forming an annular cylindrical mass, whose interior hollow is of 72 feet, and the thickness of the ring of 12 feet. It is coated outwardly with granite on all its circumference, and its upper platform is also of granite. Finally, the piers can be undertaken independent of the other works. The first operation will be to sink in the channel comprised between their two sides, and in all the space they occupy, a flooring intended to level the bed excavated by the dredges, and to connect the two piers by a common base. This flooring, the bottom of which is full and the upper part formed by a trellis filled with béton, will be sunk to the bottom by panels of 25 feet; once leveled by means of concrete blocks of béton having 4 feet height, 24 feet in the direction perpendicular to the axis, and 10 feet parallel thereto, will be sunk at 50 feet distance on the right and left of the axis of the canal. These blocks are hollow, and their sides are one foot thick; they may, if necessary, and for the better strengthening, be filled with earth. The face of the canal is slightly inclined. The two upper layers will only have 22 feet, offering a decrease of 2 feet on the sea-side; this graded deduction will extend to the water-line, where the length of the blocks will only be of 18 feet. The 10 feet of pier from the water-line to the level of the lateral walls of the sluice will be constructed of bricks. In short, it will be seen that all the different points of the works may be begun simultaneously, and there is no impediment to the forming of six or seven gangs, except the assembling of so many workmen on the same spot, the difficulty of superintending such a large number, the difficulty of supplying materials, the incumbrance caused by the arrivals, and other obstacles that will be understood by practical men. It is well understood that the order of the works may be modified according to circumstances. We will pass now to the estimate of the cost of each part of this great enterprise. We must set forth here the data which have served us as a basis for the estimates at this important part of the work. After a long discussion of the analogous works performed in the ports of Toulon and Valence, on the Seine, and on the bars of the Nile, the engineers of the Suez Canal have adopted machines that not only perform the excavating, but also, by means of revolving carriers, transfer the rubbish on the bank. These machines, of 35 horse-power, working 250 days per year, can excavate 375,000 cubic yards, at an average cost of 20 cents. The 50 horse-power engines will work at the rate of 30 cents per cubic yard. The work of the opening of the channel is to be done, as stated, in prairie-land for a distance of 21,580 feet, and in lagoons for 10,500 feet, on an average depth of 2 feet. During all this passage through the lagoons it is necessary to perform, on each side of the canal, a casing made of piles and boards, rising to the height of 3 feet above high-water mark, and preventing the sea from washing off the rubbish that is to form the banquettes and levee. This work is necessary in order to allow the levee to settle and consolidate. $259, 621 The digging through prairie-land will cost.. The making of the levees, both in prairies and lagoons.. $300, 140 182, 004 620,588 We cannot pass silently the result of the calculation of filling as compared with the excavating. We had indicated, as a basis perfectly sufficient for the solidity of the levee, a length of 600 feet; that is 22 feet of base on each side, for a height of 10 feet; but the disposable rubbish will enable us, while leaving the slope on the canal-side, to extend the base on the outer side as far as 120 feet from the banquette, which will give a nearly horizontal talus, and relieve us of all fears of the action of the sea, even in the hurricane. SECTION 3.-Sea-side sluice, (excavating already comprised in embankments in the preceding chapter :) SECTION 5.-Accessory works and appendages: fresh-water ditch, warehouse, workshop. Draining-machine of 30 horse-power, placed on a boat. Three dredge-boats of 35 horse-power, $12,000 each Inferior flooring and concrete filling Temporary wood-work for constraction of piers. Masonry, concrete works, bricks, granite heads of 200 feet both inside and outside, say 800 feet.... Mole.-Masonry and filling, granite facings... Temporary building for the workmen, diving-bell, pumps, and Six boats for driving piles, at $1,600 each. 151, 124 45,000 646, 197 50,188 1,000, 093 $20,000 8,000 9,600 36,000 Two dredge-boats of 50 horse-power, $18,000 each 36,000 Cost of tools and instruments, at 10 per cent. on first cost 30,000 70,000 Two locomotives.. 20,000 Sundry buildings, administrator's house, lock-tenders' houses, stores, depots, workshop for the machinery, &c.. 35,000 264, 600 The capital strictly necessary, resulting from what precedes, must therefore be of... -$2, 221, 569 But it would not be prudent, in bydraulic 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.... 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-limit 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 connect 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 plane, formed of argillosiliceous 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. 2.-Report of Board of Engineers upon Captain Howell's project for a shipcanal 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 waters thereof, of suitable location and dimensions for military, naval, and commercial purposes, 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 St. 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 consideration, 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 St. Philip, both heavy structures, resting upon an alluvial formation in all respects similar to that through and upon which the canal would have to be constructed. The Southwest Pass was also visited, and the working of the dredgeboat 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 engi. neering within the last twenty-five years, but, more particularly and pertinently, from the character of the borings made by Captain Howell upon the Fort St. Philip peninsula, across which the proposed canal 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 |