further from Saint Louis. The cost of such a steamer as is needed would be not less than $30,000.

Assuming that in answer to the demands of the commercial and producing interests the improvement of the navigation of the Mississippi is to be undertaken, it would be advisable on the score of economy to adopt the policy that the United States should own the principal working appliances which must be used, such as pile-drivers, dredges, and possibly barges and tow-boats for the transportion of materials. Even if the contract system is adhered to, it is found much more economical to provide the equipment, which as representing a fixed capital must be paid for either in increased prices for work or by direct purchase.

Government owning the equipment an extended competition may always be expected. In the other case the amount of fixed capital required will restrict the competition to very narrow limits, and put the work at the mercy of combinations.

The following shows the financial condition of the improvement at the close of the fiscal year, and the amount recommended for the year ending June 30, 1875:

Amount appropriated March 3, 1873..

Amount expended during the fiscal year ending June 30, 1873..

Amount available July 1, 1873......

198,550 00

Additional amount required for the fiscal year ending June 30, 1875, for improvement of the Mississippi River from the Missouri to the Ohio River....

$600,000 00

Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount.

Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount. Price. Amount.

K 3.

IMPROVEMENT OF THE MISSISSIPPI RIVER BETWEEN THE MOUTHS OF THE MISSOURI AND MERAMEC RIVERS.

The work was undertaken in accordance with the recommendations contained in the report of the Board of Engineers, dated April 13, 1872, and concurred in by the Chief of Engineers. The Board recommended the protection of a portion of Sawyer Bend, and the raising an extension of the two Venice Dikes and the Long Dike within the limits of the harbor of Saint Louis.

It was decided to do the work mainly by contract, and advertisements were issued inviting proposals. Bids for furnishing and delivery of material in Sawyer and Venice Bends were opened on the 10th of September, and contract awarded to the Grafton Stone and Transportation Company, they being lowest, as may be seen by the abstract of proposals given below.

It was intended to perform all the grading necessary, by hired labor, but as the workmen of the Government would then be working under the 8-hour law and those of the contractors would not be within its provisions, it was deemed best to do this by contract also, and proposals were therefore invited for the removal of 75,000 cubic yards, more or less of earth, spreading of 3,300 squares of Macadam and other labor, as well as unclassified labor. The contract was awarded to Mr. Willard Johnson, of Fulton, N. Y., as per abstract accompanying this report, he being the lowest bidder.

The nature of the work as well as its extent for the year is given in the following, quoted from the report of Mr. R. E. McMath, principal civil assistant on this work, dated July 10, 1873:

Preliminary surveys were made during August, to determine location of lines and detail of plans.

For the work at Sawyer Bend it was decided to commence at the foot of Grand avenue, and carry the protection up stream as far as the means will allow. The use of brush in foundations to prevent the stone from sinking indefinitely in the underlying sand was thought best, though such use for this purpose and at such a place was to some extent an experiment. Before examination of the locality it had been proposed to protect the bank by a system of spur-dikes below low water, and a continuous revetment of the slope above. As that system still has its advocates it may be well to state the grounds for the preference of a continuous longitudinal dike as a foundation for the revetment.

The spur-dikes as proposed were to be 150 feet apart, 50 feet in length and 6 feet high, each spur being expected to protect three times its length, an expectation founded on experience, but not considering that these dikes would be submerged, and therefore very unlike jetties when the current sweeps around the end but does not run over.

In the case of submerged wiers, the action of the eddy below is well known to be sufficient to require an extension of the abutments down stream, and this is a similar

case.

h

Another fallacy in the theory of spur-dikes, as suggested for this locality, is apparent on consideration of the effective length which is a horizontal line, therefore if the dike be of uniform height, resting on a slope, the expression for the effective length would be effective L= or wholly independent in the length of dike, which only can enter as a limitation, when sine slope becomes very small, showing that the theory is only applicable in cases of level bottom.

S

The underwater slope at Sawyer Bend was found to be about 2 horizontal to 1 perpendicular until a depth of 18 feet was reached, when it became nearly level, consequently the spur-dikes, aside from the first objection, would have to be at least 18 feet high at the outer end to make their effective length answer the conditions, and in that case the cost would exceed that of the longitudinal dike adopted.

The plan adopted was to excavate, where necessary, a trench to the depth of 8 feet below lowest water, and fill it with brush in crossed courses, the tops reaching outward as far as practicable, to form a mat to protect the base from scour; on the brush,

riprap is placed until it appears at mean low water, which was assumed at 5.6 above lowest low water, the rip-rap forming the base of the revetted slope.

After a discussion of various slopes, that of 2 horizontal to 1 perpendicular was adopted, chiefly as that furnished material for the grading better than any other.

The detail of plan is the same as for the wings of the abutments at the Alton dam. Work was begun October 13, 1872, and except when suspended on account of ice, or delay in furnishing material, continued until June 30, 1873, when it was completed so far as is practicable at the present stage of water.

The length protected is 1,475 feet, of which 1,118 feet is revetted; the remainder is protected by cross-dikes.

The latter method was adopted as a temporary expedient to protect the work, but having proved itself a complete protection of the bank, equally efficacious and less costly than revetment, it is proposed to continue the protection by cross-dikes in future and abandon the revetment.

Of the original distance of two miles 1,475 feet are now complete; 1,450 feet has been undertaken by the board of water commissioners for the city of Saint Louis, leaving 7,635 feet to be done, towards which we have an available balance of $13,883.98 from allotment of $50,000 of appropriation by act dated June 10, 1872, and $50,000 from appropriation dated March 3, 1873.

A contract has been recently awarded to Thomas M. Hackett for continuation of the work under the late appropriation.

The balance of the former is to be relet.

VENICE BEND.

Raising and extension of Long Dike is in continuation of an old work begun by the city of Saint Louis, the old dike being 1,460 feet long and generally 6 feet above lowest water. Work was begun October 4, 1872, and progressed slowly until about onethird of the length was raised 7 feet, when the contractor ceased delivering stone, as the depth of water at the dike was insuflicient for his barges.

In November an effort was made to extend the dike, but the contractor did not deliver any material until the 12th, and then a severe storm, followed by a run of heavy ice, prevented its use until the 22d, when the brush was laid upon the ice as a last resort, a dangerous experiment, but being favored by good weather the riprap was put on and the brush sunk; the section put down was 130 feet long by 30 feet wide; it being at the end of the dike, where usually the sand is scoured out in the winter to a depth of 30 feet or more, it has been exposed to a severe test of the efficiency of brush foundations. When examined in February last, after the ice ran out, it was uninjured. The sand accumulating at the end of the dike in high water, and scouring out at low, (a change of 20 feet being shown from August to November,) it is scarce to be regretted that we did not succeed in accomplishing more last season, as if resumed in August this year the extension will require but a fraction of the material which would have been used last fall, and the portion done is meanwhile being tested.

The extension proposed is essentially the same in plan as the Alton dam.

The amount expended on account of this work has been $8,615, leaving a balance of $41,385 available for further work out of the $50,000 allotted for the work at this locality.

Former contracts terminating July 1, the work is to be relet under amended specifications.

The balance just stated is all that can be profitably expended this season, and so far as I can now judge will be more than sufficient to complete the raising and extension of Long Dike.