ported by the water upon the dry bars and other portions of the presen not embraced within the limits of the proposed low-water channel. The mate effect sought to be produced by such deposits is a comparative unifor in the width of the high-water channel of the river.

It is believed that the works estimated for in this report will create t establish a depth of at least 10 feet at extreme low stages of the river ove the bars below Cairo, where they are located.

It is the opinion of this Commission that, as a general rule, the cha should be fixed and maintained in its present location, and that no atte should be made to straighten the river or to shorten it by cut-offs.

The borings which were made in 1879 at New Madrid and Plum Point, ¦ direction of the Board of Engineers, for the improvement of the low-w navigation of the Mississippi River below Cairo, and those of more recent d at Memphis and Helena, made under the orders of this Commission, as well a those near Lake Borgne, reported by the levee commission of 1875, and oth made along the proposed line of the Fort Saint Philip Canal, and the artes well sunk at New Orleans, all furnished concurrent evidence of the yield character of the strata forming the river-bed. This evidence, taken in connect with the fact that deep water is found in all the bends of the river where t width is not excessive, and that these bends have, by their shiftings at one ti or another, probably occupied and covered nearly every part of the belt fr 10 to 20 miles in width from Cairo to the Gulf, point to the conclusion, if does not indeed justify it, that there is no extensive stratum of mater capable of resisting erosion and preventing the river from deepening its o bed. In exceptional localities where the material is too tough or the grate too heavy for removal by scour, dredging may have to be resorted to as a auxiliary, the depth secured by this means being maintained by the work erected for narrowing the stream.

Experience, as well in this country as in Europe, justifies the belief that the requisite correction and equalization of the transverse profile of the stream by developing new shore-lines and building up new banks, may be made chied through the instrumentalities of light, flexible, and comparatively inexpensive constructions of poles and brush, and materials of like character. These con structions will commonly be open or permeable to such degree that, without too violently arresting the flow of water, thereby unduly increasing the head and causing dangerous underscour, they will sufficiently check the current to induce a deposit of silt in selected localities.

The works which have been used in similar improvements are of various forms and devices, such as the hurdle, composed of a line of stakes or light piles, with brush interlaced; the open dike, formed of stakes with waling strips on both sides filled in loosely with brush; the continuous brush mattress, built or woven on fixed or floating ways and launched as fast as completed, as a revetment to a caving bank, the mattress used as a vertical or inclined curtain, placed in the stream to check the current, the same laid flat on the bottom as the foundation for such a curtain or as an anchorage for other brush devices; curtains of wire or brush netting, placed vertically or inclined in the stream; and various other forms of permeable brush dikes, jetties, or revetments. Some of these methods of construction have been used on the Mississippi and Missouri rivers with increasing satisfaction and success, although they can not

yet be regarded as entirely beyond the experimental stage. In some, perhaps in many localities, works of a much more solid character than those above indicated may be necessary.

The closure of deep channels or low-water chutes, with a view of confining the flow to a single passage, may require substantial dams of brush and riprap stone or gravel, but it is believed the lighter and less costly works will generally suffice.

By a permeable dike located upon the new shore-line to be developed, connected with the old bank at suitable intervals by cross-lines of like character, or by jetties of hurdles or other permeable works projecting from the bank with their channel ends terminating on the margin to the proposed water-way, or by any other equivalent works, the area to be reclaimed and raised will be converted into a series of silting basins, from which the water, flowing through the barriers with diminished velocity, will, after depositing its heavier material, pass off and give place to a new supply. In this manner the accretion will go on continuously through the high-water season, or through two or more seasons if necessary, the works being renewed on the higher level as occasion requires. Wherever necessary, the new bank must be protected by a mattress, revetment, or some equivalent device.

That these methods of improvement are practicable, is shown by the works already executed on the Mississippi and Missouri rivers.

*

*

The plan submitted by the Board of Engineers for the improvement of the low-water navigation of the river below Cairo, in their report dated January 25, 1879, in which it is recommended that $600,000 be asked for the improvement of the Plum Point Reach, and "that the improvement be effected by narrowing the shoal and wide portions of the low-water river to about 3,500 feet, and by protecting caving banks where necessary," is substantially adopted for the initial works submitted for construction in this report.

An accurate estimate of the cost of properly improving the entire river below Cairo can not be made until after the completion of the surveys now in progress. Moreover, estimates based upon the latest data from those surveys will doubtless require modification in some particulars, to meet subsequent changes in the river, and will perhaps be considerably reduced in the aggregate amount by improved methods of construction developed during the progress of the work.

From this it appears that the work to be done consisted of two kinds; first, and most important, contraction work, to narrow the river where too wide, and, secondly, bank revetment, to prevent the banks from caving and thus widening the river again. The methods of doing this work and the means to be adopted are briefly outlined above, and, as will be noted, all the contraction work was intended to be comparatively light and easy of construction and of small cost, and it might be well to state here that the Commission and, in fact, all the boards that had investigated the subject, vastly underestimated the hydraulic forces to be contended with on this river and the means necessary to control these forces.

For the improvement of the Mississippi River in accordanc the plans of the Commission, Congress made the first appr tion in March, 1881. Preparations were at once begun, and art work was started late in that year. This work has consisted of traction work and bank revetment, and these two subjects wil later discussed in detail.

For a few years the work went on quite smoothly, with reg and liberal appropriations, but two facts were soon devel first, that the light construction works originally designed much too weak and that the cost of the improvement would much greater than had been originally estimated; and, see that one of the first results of contraction work was to increa bank caving and that generally bank revetment was of greater r ative importance than it had at first been considered. Con quently larger allotments were made for revetting bank, this to done in connection with contraction works.

The first interruption to the work came in 1885 from a failure. an appropriation bill to become a law, and when the next bill. finally passed in 1886, it contained the following clause prohibiti bank protection:

And provided further, That no works of bank protection or revetment sta be executed in said reaches or elsewhere until after it shall be found that th completion of the permeable contracting works and uniform width of the hig water channel will not secure the desired stability of the river banks: P vided, however, That nothing herein contained shall prevent the constructi of revetment work where the banks are caving at Greenville Reach, Delta Poir. in front of the cities of Vicksburg, Memphis, Hickman, and Columbus: And provided further, That contraction works shall be built at the same time in the wide portions of the river immediately above said revetment works.

The reasons for the insertion of this clause were afterwards stated to the Commission by a prominent Congressman to have been substantially:

The object of the act creating the Commission was for the purpose of hav ing the river treated as one great whole, in order that works placed and built should form part of a scheme relating not alone to a given locality, but in rela tion to the necessity of the entire stream, and as parts of the same connected system. It is not the intention of Congress to dictate the plans for the im provement of the river; it could not do so even if it would, and when it became necessary for Congress to attempt this, the raison d'etre for the Commission ceased to exist. The Commission, early in its existence, formulated a plan which was accepted and confirmed by Congress, but it was now felt that the Commission was getting away from its plan, and was constructing works of

t

reat cost outside that plan; works which were subject to great injury and oss, and not effective in producing the results sought for. Congress desired o put a stop to this, and hence, these prohibitions in regard to works of bank rotection or bank revetment. It was intended that that kind of work should ease. It was intended to absolutely prohibit the continuation of bank protection or bank revetment in Lake Providence and Plum Point reaches; for, why construct works requiring such large sums of money when less expensive methods would do? It was decided to make the trial, taking the risks of the works being taken away.

After a consideration of the matter, the Commission made and submitted its projects for the expenditure of this appropriation, but these projects were not satisfactory to the Department where the prohibitory clause was more strictly interpreted. Owing to the trouble over the interpretation of this clause, none of the plans for channel work were approved by the Department, and the funds I were finally allotted and used for levee construction. This matter of the prohibitory clause with its attending circumstances is well explained in the Report of the Chief of Engineers for 1887, page 2759.

In 1888 a new appropriation became available without such a prohibitory clause, but as the bill did not become a law until August, and on account of the repairs to plant, which by this time were badly needed, it was very late in the season before actual work could begin.

Thus it will be seen that four successive working seasons were practically lost. This was certainly most unfortunate, for the work was at that time in a critical condition, some portions partly completed, some in need of repair, and other portions, though in themselves complete, yet requiring additional work to enable them to act efficiently. In all cases the damage from this delay was very great, and in some it meant the almost complete loss of all previous work and the results accomplished by it. By the time funds were again available time enough had elapsed to show the effects of the various works that had been constructed. When work had been first begun, the prominent idea had been to narrow the river where too wide, with bank revetment as a secondary consideration. The contraction works had been built and had closed the chutes at least partially and had built up bars and had thus narrowed the river, but the river had at once started to widen itself once more by cutting away its banks. Attention was thus called to the great importance

of bank revetment, and in their report of 1859 the Commer warted the following:

Herefore the work of the Commisja had been largely confined · speria, Marbes where navigation was un2sually diffruit, and where th bity of the work of the improvement eusid be thoroughly tested and yto be country estimated. This work is still incomplete, altblagi its fac and vase Lave, it is bought, been fairly demonstrated. It is, however, m derwood now that it is likely to prove a slower process than was st fivel posed; that the work can not be hurried, but must be gradual and progres This gives an opportunity for considering many questions which at fire been set aside, owing to the paramount necessity of testing the main featurett the proposed work. Nothing during the progress of the work has been sunt: oughly demonstrated as the great importance to be assigned to bank prote as a factor in the general improvement, as well as the impossibility of amen plishing the desired result in any other way. Recent action by Congres certain special cases shows that this fact is fully recognized, and the Com sion desire to call attention to the fact that there are very many places whe the general, rather than local interests, demand prompt action. Promine among these are localities where the continued eaving of narrow necks thre ens in the near future the formation of cut-offs with their well-known dise trous effects, and also places where the caving-in of levees across the ends old cut off lakes will render it necessary to go back of these lakes with long a expensive lines of levees in order to carry out the system of control of fix discharge that the Commission have undertaken.

Work having been once again started, after the long interruption, proceeded smoothly, bank protection being now considered f prime importance and contraction works being restricted to the repair and completion of work already under way. One new feat ure of the work became about this time of importance, and that was the custom of inserting in appropriation bills clauses allotting funds specifically to the protection of the banks at special localities. cities, towns, etc.

The experience with the revetment work previously done had shown it to be inadequate for the purpose, and rapid changes of type were now made until there was developed the standard of the present day: A fascine subaqueous mattress with upper bank pav ing of stone. But as the revetment work had gradually been increased in strength, it had also increased in cost, until in the new standard type the cost had reached about $30 per linear foot of bank, or approximately $150,000 per mile.

As the large cost of a systematic improvement of the whole river became evident, the Commission was led to investigate means for