The iron is of the finest quality, one specimen (the first) bearing a tensile strain of 21,500 pounds, while the second specimen required 29,000 pounds to the square inch to break it.

Some few items have been obtained in open market during the year, but not of sufficient account to mention in this report.

PLANING.

The contractors, Messrs. Copeland, Gray & McClelland, have finished their contract during the past year, having performed the following amount of work, with entire satisfaction to myself, up to the 17th day of November, 1870, when they completed their contract: 113,390.66 feet, board measure.

TIMBER.

The contract for timber for the lock-gates was given, on the 10th day of March, 1870, to James Carroll. On August 16th he completed his contract, having furnished of the finest quality of white oak timber the following amount: 125,179.7 feet, board measure.

For the completion of the improvements at this place I estimate that $1,000,000 will be necessary, all of which could be employed during the year ending June 30, 1873. In fact, it would be of great monetary advantage to the Government if the necessary funds for completing the work could be furnished immediately, instead of by small annual installments. So much has been already said on this subject and on the absolute necessity of completing the work immediately, that I will not enlarge upon them in this report.

In closing I must express my thanks to all my civil assistants, especially Mr. E. H. Worrell and Mr. J. E. Griffith, for their cordial cooperations in my endeavors to forward the progress of the work. The following is an abstract of contracts made during the fiscal year:

Statement of cash received, expended, and remaining on hand during the

fiscal year ending June 30, 1871.

All of which is respectfully submitted by your most obedient servant,

A. H. BURNHAM,

Captain, Corps of Engineers, Brevet Major, U. S. A.

Colonel J. N. MACOMB,

Corps of Engineers, U. S. A., Rock Island, Illinois.

H 5.

UNITED STATES ENGINEER Office,

Rock Island, Illinois, September 1, 1871.

COLONEL: I have the honor to submit the following report of the operations for the year ending June 30, 1871, pertaining to the improvement of the Rock Island Rapids of the Mississippi River.

Brevet Major Charles J. Allen, captain Corps of Engineers, was in local charge at these rapids, under the superintendence of Brevet Major General J. H. Wilson, United States Army, and under him the work was progressing as follows:

OF THE COFFER-DAM AT CAMPBELL'S CHAIN.

The excavation at this chain was finished during the year ending June 30, 1870. Very little had been carried off by the ice and high water, and it was, therefore, necessary in order to give to navigation a clear channel of at least 200 feet in width and 4 feet in depth below low water of 1864, to remove all obstructions. In July, chisel and dredge were set to work at this chain, and at the head and foot of the dam. All cribs, portions of dam, piles of loose stones, and patches of rock upon which the dam had been resting, were removed, and thereby the proper width and depth of the channel obtained. That side of the dam running parallel with the stream from head to foot of dam was left standing for the purpose of throwing more water into the excavated channel, and to serve as a guide to pilots. With the same intention, those parts of the dam running out from the shore to the channel, above and below, were left in their places. Above the dam some rock, broken by the chisel in the year previous, was dredged up, and also a small patch below the dam was chiseled and removed by dredge.

The "Little Sycamore" dam was also standing, and this also had to be dredged up, and the rock upon which it rested chiseled off, and a clear channel given to navigation.

At "Big Sycamore" dam the obstructing cribs at the head and side of the dam, together with the largest portion of the dam, were removed, and a good entrance to the channel above and below obtained thereby. In the month of September, chisel and dredge had finished their work, and the following quantities of rock were estimated to have been removed:

At Campbell's Chain.

At Sycamore Chain..

858.12 cubic yards. 245.18 cubic yards.

This was the last excavation undertaken by the firm of Case & Co.

On the 1st of October Brevet Major General J. H. Wilson was relieved from duty as general superintendent of the Rock Island Rapids improvement, and this office assigned to your charge. In the same month Brevet Major C. J. Allen was transferred to the office of General Raynolds, and ordered to St. Louis, Missouri.

Under your superintendence new bids for improving these rapids were received, and on the 16th of October the lowest bidder, Mr. Elliott Harroun, was awarded the contract, and the same signed in the latter part of November.

As the season had advanced so much that the commencement of work at Smith's Chain (the next important chain) seemed not advisable, the improvement of this chain was postponed till the spring of 1871. In the month of January, 1871, the new contractor, Mr. Elliott Har

roun, died, and his heirs and partners prayed to be released from the contract. This was granted to them, and on the 13th of May new advertisements for proposals were published. On the 19th of June the lowest bidder, Mr. J. J. Dull, was awarded the contract, which was signed July 11, 1871.

You are aware, colonel, that the former contracts were silent concerning the payment or non-payment for the "below-bottom" excavation. This caused a great deal of trouble with the contractors, and was a source of unforeseen expense to the Government. To avoid in future similar misunderstandings, you ordered the following paragraph to be inserted in the advertisement for new proposals:

The grade for the bottom excavation is a plane 4 feet below low water of 1864; any excavation below said grade, occasioned by stratification or carelessness of workmen, will not be paid for.

According to this sentence any controversy will in future be removed, and the work on the part of the Government be facilitated. In former years the contractors did not care to keep the plane of grade, knowing that they would be paid for the "below-bottom" excavation, but now they may go as deep as they please, no more than the amount of rock found by careful and minute measurements and calculations upon the plane 4 feet below low water will be paid for to the contractors.

Soon after signing the contract, Mr. J. J. Dull commenced building a coffer-dam at Smith's Chain, 900 feet by 250, and excavation in the pit is now in a fair state of progress.

At the present time a second coffer-dam, at the so-called "opening of Smith's Chain," has been commenced, and will be completed in about one week. Two chisels are working on a patch above the first-mentioned coffer-dam.

It is proposed, as soon as the work at Smith's Chain is finished, to improve, before the close of navigation, patches between Sycamore and Smith's Chains, also patches near Crab Island and St. Louis Chains.

The engineering work done by me and my assistants, Messrs. C. J. Pauli and C. H. Beuck, was as follows:

A dispute about quantities of rock to be paid to contractors at certain chains having arisen between them and the Government, a claim of the contractors, Case & Co., is now pending in the United States Court of Claims, and nearly my whole time, together with that of my assistants, has been occupied in investigating the grounds of this dispute and reporting upon it.

During the months of August and September, 1870, extensive soundings, which your predecessor deemed necesssry, were made for this investigation.

These soundings were made

1. In the channel at Duck Creek Chain.

2. In the upper part of channel at Moline Chain.

3. In the channel at Campbell's Chain.

4. In the channel at Sycamore Chain.

Soundings were also taken on patches above Sycamore Chain and on Smith's Chain to complete the maps made in 1867; 4,300 theodolitebearings, 4,300 compass-bearings, and 68,000 soundings were taken on these various places.

The soundings of Campbell's, Moline, Duck Creek, and Sycamore Chains were platted with a protractor in the month of October on common paper, and afterward, during the winter months, calculations of bearings and plottings of soundings by abscissas and ordinates were

undertaken, together with a minute report, investigation, and various calculations concerning the above-mentioned dispute.

In the beginning of June this work, together with the following maps, was completed:

One large map of Smith's Chain, (sound-map,) 79.2 inches=1 mile, 43 by 6 feet.

One large map of Smith's Chain, (sister-map,) 79.2 inches=1 mile, 43 by 6 feet.

One

large map of Sycamore Chain, (sound-map,) 84.48 inches=1 mile, 4 by 7 feet.

One large map of Campbell's Chain, (sound-map,) 79.2 inches=1 mile, 4 by 7 feet.

One large map of Duck-Creek Chain, (sound-map,) 84.48 inches= 1 mile, 43 by 7 feet.

One large map of Sycamore Chain, (sound-map,) 84.48 inches=1 mile, 4 by 7 feet.

One large map of Campbell's Chain, 79.2 inches=1 mile, 4 by 7 feet. (Last two on common paper.)

One map of Sycamore Chain, showing "below-bottom" excavation, 84.48 inches 1 mile.

One map of Campbell's Chain, showing "below-bottom" excavation, 79.2 inches 1 mile.

One map of Duck Creek Chain, showing "below-bottom" excavation, 84.48 inches 1 mile.

One compilation, showing surface of excavation according to survey in the pit, and according to sounding-maps at five different chains. One map of Sycamore Chain, showing "below-bottom" excavation. One map of Campbell's Chain, showing "below-bottom" excavation. One map of Campbell's Chain, showing "below-bottom" excavation. One map of Sycamore Chain, showing profiles in the channel. One map of Campbell's Chain, showing profiles in the channel. One map showing places to be improved for the final completion of the work at the rapids.

One general map of the Rock Island Rapids.

One field-map of Smith's Chain, 79.2 inches=1 mile, 5 by 3 feet. One field-map of patches between Sycamore and Smith's Chains, 84.48 inches=1 mile, 5 by 3 feet.

One tracing of the map of Smith's Chain.

Several sketches attached to certain reports of the year 1870.

Besides these maps, the force of the office was engaged in preparing the evidence in relation to certain claims filed in the Court of Claims against the United States, a work which occupied four months. All of which is respectfully submitted.

Colonel J. N. MACOMB,

E. F. HOFFMAN,

Civil Engineer Assistant.

Corps of Engineers, U. S. A.

P. L. Mitchell and William Eg. gleston, Rock Island, Ill.