SURVEYS AND RESURVEYS.

During the past year no extended surveys have been made. A change in the method of conducting them puts it in the power of the regular engineer party employed to lay out and direct the work, to make very elaborate surveys, which heretofore required a large party; and now the soundings are taken immediately in advance of the dredging, therefore the only surveys have been of the bars worked on.

A large amount of material on hand at the beginning of the year has been worked up and plotted on the several scales required for working and record sheets.

In working up the results of the surveys of June, 1870, my attention was drawn to the numerous errors made in reading and recording depths measured by hand, and the failure to develop the shape of the bottom by detached surroundings; also, it was found a very laborious matter to test the excavated channel for lumps and ridges.

These considerations led me to study the problem of mechanical sounding under the conditions noted; the result was a machine working on the principle of the pantagraph, recording a continuous profile of the ground passed over, which, being applied to the system of pontons already in use, gave satisfactory results, and after being fully tested, the machine was purchased for the Government on your recommendation.

The machine not only gives better results than hand labor, but greatly reduces the expense for field and office work. Tested both by crossings, duplications, and by comparison with rod soundings, the results are always correct.

WORK REQUIRED TO COMPLETE THE IMPROVEMENT.

Whatever may be said in favor of a slack-water improvement, in connection with the enlargement of the Illinois and Michigan Canal, considered as a military or naval measure, or in view of a possible development of commerce over the line, there can be no dispute that, until the canal is complete, an open channel of 4 feet depth is ample to satisfy the trade, and, as a canal project would be the work of many years, it is my opinion that to foster the trade by opening and maintaining a good channel equal to the present canal is all that can now reasonably be asked of the General Government.

Former reports, recommending a much more costly improvement, contain arguments which may safely be referred to, to justify a less expensive one, such as is now in progress, and which can be completed according to the following estimate, covering the entire river now unimproved:

ESTIMATE.

The estimate is made for a channel 150 feet wide and 43 feet deep in excavation, with dams to confine the water when required.

1,305,040 cubic yards dredging, at 25 cents per yard.

15,012 cubic yards dams, at $2 per yard Engineering and contingencies...

Total estimated cost....

Deduct present appropriation

$326,260 00 30, 024 00 35, 628 40

391, 912 40

Balance to be appropriated...

100, 000 00

291, 912 40

of which $150,000 could be profitably expended during the coming fiscal year.

The foregoing estimate is made for the improvement of West Point chute at Grand Island; and as to make the improvement permanent it would be necessary to close the Bath chute, which, as the traffic at Bath is inconsiderable, might properly be done, locating the dam near the lower end of the island would give a good slack-water navigation from the head of the island to all the points needing any accommodation,

and relieve the general trade from the disadvantage of navigating a very narrow and crooked channel, and the Government of the additional expense of over $30,000, which would be required to make 4 feet depth in the Bath chute.

As there would doubtless be local opposition to the proposed plan, it would be desirable for the formal authority of Congress to be given in the appropriation bill.

As (if the plan is to be carried out by classification) Grand Island would come into the class next to be put under contract, the attention of the Department is respectfully invited to secure the authority the coming session.

WHAT IT WILL ACCOMPLISH.

The amount asked for next year will be sufficient to make a 3-foot navigation throughout the river by the removal of the following bars: 1. Lancaster Flats.

2. Canton Landing. 3. Grand Island. 4. Sugar Creek. 5. Indian Creek. 6. Gar Island. 7. Bevington. 8. Buckhorn. 9. Grand Pass. 10. Otwell's. 11. School-House. 12. Apple Creek. 13. French.

14. Bloom's Landing.

15. Six-mile Island.

PUBLIC UTILITY.

The public utility of the improvement is by no means to be measured by the amount of trade actually passing over the river, which, of itself, is sufficient to justify all that is now asked, but there is an indirect influence which cannot be expressed in figures, exerted in moderating transportation charges over competing railroads. In the direct and indirect influences of the improvement, the whole of the region reached by the Mississippi and its branches is more or less interested, according to the extent of the commerce with the North and Northeast.

MAINTENANCE AFTER COMPLETION.

The most economical mode of maintenance would be for the Government to do the necessary work without contracts, to do which would require a first outlay of $20,000 for machinery and boats, and an annual appropriation of $8,000 for working expenses. To do the same by contract would require $12,000 annually.

The river lies in several collection districts, (internal revenue,) whose designation and amount of collections are unknown at this office. The nearest port of entry is St. Louis, but the amount of revenue collected during the year is not known.

Very respectfully, your obedient servant,

ROBERT E. McMATH,
Civil Engineer Assistant.

Colonel J. N. MACOMB, Rock Island, Ill.

Abstract of proposals received at the United States engineer office, Peoria, Illinois, October 6, 1870, for furnishing materials and doing all the work for the improvement of the Illinois River, according to advertisement dated September 3, 1870.

* Rate per cubic foot.

Per cubic yard.

J. N. MACOMB,

Colonel Engineers, U. S. A., General Superintendent United States Improvement Illinois River.

Abstract of contracts entered into during the fiscal year ending June 30, 1871, for the improvement of the Illinois River.

Colonel Engineers, U. S. A., General Superintendent U. S. Improvements on Illinois River.

Dredging and con-
structing riprap and
other dams, between
Copperas Creek and
the mouth of the Illi-
nois River.

$100,000 After deducting

H 4.

UNITED STATES ENGINEER OFFICE,

Keokuk, Iowa, August 1, 1871.

COLONEL: I have the honor to submit to you the following report of the operations performed on improvements of the Des Moines Rapids for the fiscal year ending June 30, 1871.

SECTION WORK.

From an application made on May 23, 1870, permission was granted to extend the contract of Messrs. Dull & Williams to take effect July 12, covering the sum of $250,000. The contractors pushed forward the work immediately, and performed the following amount of labor up to November 9, the date of closing the contract: One and a half miles bailing and draining; 124,685.70 cubic yards excavation of earth; 80,792.90 cubic yards excavation of rock; 4,155.00 cubic yards embankment grading railroad track; 156.00 cubic yards labor of puddling; 12,813.60 cubic yards face stone in riprap walls. These quantities have been distributed along the line of the canal wherever it has seemed necessary and proper in the eyes of myself, under the direction of General J. H. Wilson, until September 30, 1870, and since that time of yourself. In July, 1870, 3,152 cubic yards of embankment were made on the Chicago, Burlington and Quincy Railroad, completing this portion of the work, rendered necessary by the location of the middle lock, and the raising of the high water in the canal above the old grade of the track, &c. In September much delay was experienced on account of the sudden rise in the river; however, no damage was done to the work further than the delay occasioned, which, by comparison of the estimates for this month and the preceding, was about 25 per cent.

On November 1 I directed the contractors to discontinue the excavation of the rock and put the entire force into earth, so as to close, as far as the funds available would permit, the gap existing in the embankment above the lower lock. This was accomplished, and no trouble was experienced during the winter and spring, as we were fortunate enough to have a comparatively low stage of water until the work recommenced in February, under the special appropriation of $341,000, made January 18, 1871. Approximate estimates were made daily, in order to keep the work within the limits of the funds available, and yet obtain as much work as possible. By this rate I stopped all work on November 9, and found that I had really allowed the contractors to work