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I transmit herewith a diagram showing the daily oscillations of the river at the place where the party was. It may be considered a mean curve for the vicinity between Helena and Providence.

The following are the checks furnished for the levels. The profiles are plotted without change, but on the maps the revised mean reading is given to the benchmarks.

Starting at Nibblet's, with bench-mark reading 98.20, the Prentiss bench-mark reads thus : Route via Vermillion Lake

105. 44 Route via Swan Lake....

106. 63 Route by river-bank...,

104, 77 Mean ...

105, 61 Starting at Grants, with bench-mark reading 100.00, the bench-mark at Wilkinson's Landing reads: Route direct from Wimbush's..

104. 42 Route via Old Port Royal.....

105. 86

Mean ......

105, 14 The accuracy of this mean determination is shown by the fact that the high-water marks on the profile from Robson's to Totten's check perfectly, the mean valve of the bench-mark at Wilkinson's Landing being adopted in placing the scale on the profile from Robson's to Delta.

By these levels the following slopes are deduced for the river-surface at high-water:
Friar's Point to Grant's—distance, thirty-four miles; fall, 11.7. feet; slope per mile,
0.34 feet.
Prentiss to Nibblet's, distance 11.5 miles..

S Fall since cut-off, 3.5 feet.
Slope per mile, 0.3 feet.

Fall before cut-off, 3.2 feet. Prentiss to Nibblet's, distance 11.5 miles..

Slope per mile, 0.28. It is to be remarked that the high-water mark at Delta is not so high by nearly half a foot as at Friar's Point, although five miles above it. This I attribute to the local influences on the mark selected of the large crevasses just above and below Delta, althongh possibly the levels may be at fault. On this account I have selected Friar's Point in preference to Delta to deduce the true fall in water-surface. The mean slope from Meniphis to Gaines's Landing is 0.32 feet per mile. (See Delta report.) Also, the crevasse at Prentiss must bave affected the high-water in 1865 sufticiently to obscure the true effect of the cut-off, which occurred on March 11, 1863.

A daily gauge-record is now kept at New Orleans by Mr. G. W. R. Bayley, city engineer, and at Cairo by the engineer of Cairo City Company.

The State of Mississippi has recently re-organized her levee system by creating a levee district of Issaqnena, Washington, and Bolivar Counties, allowing Coahoma and Tunica to join if they so elect. A levee-tax annually of 10 cents an acre and 1 cent per pound on cotton is levied for three years.

The old Delta Survey Bench No. 1, on the curb-stone near Prentiss's house, Vicksburgh, bas been moved, and is consequently now worthless.

The low-water mark of 1863 at Saint Louis was 0.5 lower than that of 1860, the lowest heretofore recorded. It was 41.3 feet below high-water in 1844, and 33.7 feet below tbe Saint Louis directrix.

At 4 p. m. of March 13 there was a furious tempest, followed during the night by as heavy a rain-storm as I ever witnessed. My party was at Friar's Point, Mississippi. At 9 a. m. of March 13 the river stood 5.2 feet below high-water of 18.55, having fallen 0.1 in the preceding twelve hours. At 9 a. m. of March 14 it was 5 feet below this flood-level, having fallen nearly an inch since daylight. No wind affected any of these readings. It is therefore evident that the rain, by its strictly local effect, raised the river at least 5 inches during this storm.

My attention was called to some singular springs in the bed of Bayou Hushpuckana. They are several in number, and some of them are located on the map. The largest of them is near the bridge. It flows freely up from several places over an extent of half

The soil is covered by a yellow, slimy deposit, with a metallic-blue scum near the rills of water, which has a decided chaly beate taste. All these springs are in the bed of the bayou, and from 20 to 30 feet below high-water level of the Mississippi. Major Severson informs me that they flow all summer, even when the river is at lowpater level, (45 feet below bigh-water,) and that the water is much colder than the water in the vicinity. Not understanding how these springs could exist in a purely alluvial region, I thought that some evidence bearing upon the age of the region might be derived from an analysis of the water and deposit. I accordingly procured samples of both, and submitted them to Dr. Charles T. Jackson, of Boston, whose reputation as a scientific chemist and geologist is well known. He gives me the following as the result of his analysis:

an acre.

Water contains in solution : Bicarbonate of lime, sulphate of lime, carbonate of iron.

Deposit consists of: Crystallized sulphate of lime, carbonate of lime, sulphide of iron, slate mud.

He considers that the spring derives its character from decomposing iron pyrites, which most probably belongs to a tertiary formation.

From the facts that none of the tertiary river-bluffs are within many miles of the locality of these springs, which are near Sunflower Landing, opposite Island 66, in the Yazoo bottom-lands; that their level corresponds with the appearance of the blue clay, and that iron pyrites can hardly be considered an alluvial deposit of the Mississippi, I think that the conclusions as to the slight depth of the alluvium in this vicinity advanced in the Delta report receive strong confirmation from the existence of these chalybeate springs.

Brevet Captain Mackenzie reports that a cut-off bas occurred at Terrapin Neck, which early in April was 300 yards wide. The newspapers, I suspect a little prematurely, reported it to have occurred on March 8, 1866. I have had every reason to be pleased with the manner in which Brevet Capt. A. Mackenzie, Corps of Engineers, and the party generally, lave labored to accomplish the ends of the survey. I am, general, very respectfully, your obedient servant,

HENRY L. ABBOT,

Major of Engineers, and Brevet Colonel, U. S. A. Maj. Gen. A. A. HUMPHREYS,

U.S. J'olunteo's.

APPENDIX N.

ANNUAL REPORT OF MAJOR WM. E. MERRILL, CORPS OF ENGINEERS, FOR THE FISCAL YEAR ENDING JUNE 30, 1874.

UNITED STATES ENGINEER OFFICE,

Cincinnati, Ohio, September 1, 1874. GENERAL: I have the honor berewith to transmit annual reports on the works under my charge for the fiscal year ending June 30, 1874.

Lieut. F. A. Maban, Corps of Engineers, has been my military assistant during the year, except from December 8, 1873, to May 14, 1874, inclusive, during which time he was on temporary duty at Savannah, Ga., under the orders of Lieut. Col. Q. A. Gillmore, Corps of Engineers. Very respectfully, your obedient servant,

WM. E. MERRILL,

Major of Engineers. Brig. Gen. A. A. HUMPHREYS,

Chief of Engineers, U. S. A.

N 1.

IMPROVEMENT OF THE OHIO RIVER. At the beginning of the fiscal year the following contracts were outstanding.

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Chartier's Creek dam, three miles below Pittsburgh.This dam was completed in August, 1873, and the contract was closed. The total amouut of stone expended under this contract was 32,480 cubic yards. It has answered its purpose satisfactorily. It closes the left channel at Brunot's Island, throwing all the water in low and ordmary stages into the Glass-honse Channel.

Wheeling dam, ninety miles below Pittsburgh.-The repairs of this clam were finished in August, 1873. They required in all 3,508 cubic yards of stone and 425 cords of brush. It closes the right or Ohio channel at Wheeling Island, thus increasing the lov.vater volume in the other channel.

Marietta Island dam, one hundred and sixty-eight miles below Pittsburgh.This dam is at the head of Marietta Island, and closes the right or Virginia Channel. The work of repairing this dam was completed in September, 1873. It required 8,301 cubic yards of stone and 177 cords of brush. It backed up the water so much more than I had ex. pected that I thought it expedient to strengthen it by a brush and pile dam below, and thus divide the fall, which at certain stages was as great as 5 feet, and was more than I considered it prudent to attempt to sustain by a dam of loose stone. I therefore bad an auxiliary dam built, whose upper line was placed 50 feet below the lower edge of the main dam, with its top surface 3 feet lower than that of the latter. This auxiliary dam was made as cheaply as possible of two rows of piles, 6 feet apart, with 30 feet between the rows, and the inclosed space was filled with brush, weighted down with stone. Some stone and brush were likewise used in protecting the banks. This auxiliary work required an expenditure of 316 piles, 5,941 cords of brusli, and 4,553 cubic yards of stone. There has been no trouble in using the right channel since the left one was closed, except occasionally at the foot and opposite the mouth of the Muskingum. This river sometimes throws out a mass of sard and sediment that occasionally troubles coalfleets. This difficulty has lately been removed by dredging.

Buffington dam and dike, two hundred and fourteen miles below Pittsburgh.--"These works were finished in September, 1873. The total amount of stone expended on both was 26,078 cubic yards.

Eransrille dike, seren hundred and eighty-three miles belou Pittsburgh. -At the close of operations in 1873, this dike bad been finished for a length from shore of 1,025 feet. I directed Mr. Charles B. Bateman, assistant engineer, the inspector of this and Henderson dikes, to examine the dike occasionally during the winter, and especially to report any effect that might be produced on the sand-bar at the upper end of the city, for the removal of which the dike was designed. He reported on the 31st of December that the deposit on the wharf from the recent rise is much less in quantity than usual; also that from the line of the highest water said deposit is clayey mud down to about the 20 foot line, from which line down it cousists of sand and gravel in patches evidently washed froin the bar.

The current during the rise and since the river has commenced falling, has been decidedly on the Indiana shore, the drift giving considerable trouble to steamers and wharf-boits at the landing

On the 30th of March he wrote: I observe that during the several rises of the past few months there has buen no deposit on the wharf below 23,50 feet on the gange at that stage, and below a strong current sweeps the Indiana shore from the water-works down-the effect, it presiuned, of the dike.

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On the 23d of May he writes:

Soundings were taken over the bar from Mulberry street to Main, when the river was at 12 feet by the gauge, and were as follows:

Feet. On highest part of the bar, opposite Mulberry street

7.50 Opposite Cherry street.

8.60 Opposite Chestunt street.

9.00 Opposite Walnut street..

10,50 Opposite Locust street...

12.00 Below Locust street, no bottom at 12 feet, showing that at least four feet has been taken off the bar during the past winter. The current on this side is stronger than before, and there is evidently a channel cut along the scour made along the bar during the winter of 1872–3.

On the 1st of June he writes :

On the bar in front of the city I made soundings, and found one little ridge opposite the water-works, near the shore, which is now four feet above low water. No other part of the bar will be more than 2.50 above low water wben dry. Opposite the foot of Maiu street, where the bar used to be, there will be six feet at low water.

The dike itself is firm and solid, and a large sand-bar has formed below it. The dike will be extended 300 feet farther during the present season. I have purposely kept this work back, in order to give the river time to accommodate itself to the new course marked out for it. A rapid construction of the dike would have caused so great a scour at its outer end as to materially increase its cost. At present the pocket behind the bar has been filled by material washed into it from the bar, and more or less of the same is scattered along the city front, making landings difficult in low water. This temporary annoyance could not have been prevented. The bar is still so high that in extreme low water it cuts off river current. When the bar is entirely washed away these troublesome deposits will depart with it. I consider this dike a marked success in its etfectiveness, its strength, and its cheapness. All future dikes in the Lower Ohio will be built in a similar manner.

Cumberland dam, nine hundred and seven miles below Pittsburgh. The repairs on this dam were completed in December, 1873, under contract with Messrs. Miller and Bedard.

The total amount of stone used was 20,187 cubic yards. Owing to the long duration of high-water last antumn, at a time when the river is usually at its lowest, it was impossible to finish this work as completely as was desired, as during the last six weeks the dam was continuously under water. I made as close a personal inspection as was practicable, and, feeling satisfied that nothing more could be done to advan. tage, closed the contract. During high-water of the winter and spring the dam was subjected to a severe test. All of the new work except a small section about 100 feet in length stood very well, but to my surprise the river lereled down a large part of the old work which had been standing for over thirty years, and was assumed to be safe and strong. During the present season I called for proposals for bringing this part of the dam up to grade, and let the new contract to Mr. Bedard, the active member of the old firm of contractors. He bid at bis old price, wbich was considerably lower than the price offered by any other bidder. Six thousand yards more will be placed in the dam, and there is reason to believe that this amount will make it safe and substantial. There will always be a strong pressure against it, as the high-water curreut is over the dam, and therefore deposits will annually form in the chute, wbich must be removed by the current as the water falls and is forced by the dam into the chute. Thus far there has been no serious trouble with the new channel at the head of Cumberland Island, but

that at the foot of the island is changeable, and will probably require some construction to fix it.

Bacon Rock, nine hundred and sixty-seven miles below Pittsburgh. This rock was formerly on the Missouri shore of the Mississippi River, but owing to the gradual change of the channel of the Mississippi it is now in the Ohio River, though a slight wash of the sand-bar between the two rivers would throw it into the Mississippi. It is a very serious obstruction in low-water. The contractors, Miller and Bedard, did notbing for the removal of tbis rock, and their contract was declared forfeited. One of their sureties, Mr. M. A. Bryson, then claimed the right to complete the contract, and his right was acknowledged. During lowwater last season he made some preparations, and waited for the water to fall before commencing work. Contrary to custom the river rose, and remained up, consequently nothing was done. During the present season, at my suggestion, he employed Capt. R. W. Dugan, of the Cincinnati Wrecking Company, to do the work for him. At the close of the year Captain Dugan had exploded, by surface-blasting, a large number of charges of dynamite on the rock, and had entirely broken up its shell. He found the interior of the rock (which is a pudding-stone) to be mainly loose gravel. This will be removed by a dredge, and before this report reaches Congress the Bacon Rock will probably be a thing of the past.

NEW CONTRACTS.

The following new contracts were made during the fiscal year just pası:

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Duck Chute, tuo miles below Pittsburgh.Duck Chute is a small channel across the bar at the head of Brunot's Island, and near the high land of the island. It is usually dry at extreme low-water. It was necessary to close it, as the current througin this opening drew coalfleets out of the channel leading into Glasshouse. The dam was finished in September, 1873, having consumed 1,995 cubic yards of stone. It entirely closed the channel across which it was built, but the pressure of water in that direction was so great as to cut out the gravel at each end of the dam, and as much water now escapes as before its construction. If the radical improvement of the Ohio be inaugurated it will probably be unnecessary to extend this dam; if the contrary be the case, its extension will be very necessary.

French Island Dike, seven hundred and sixty miles below Pittsburgh.Since the close of the fiscal year this dike has been completed, as also some slight repairs to the dike, extending down from near the foot of the island. The work has given great satisfaction to the Louisville and Henderson packets, as French Island was the shoalest place on their route. Three and a half feet is as much as I think can be depended on in extreme low-water, though the coutractor thinks he can guarantee 4 feet. A greater depth might be secured by a greater coutraction, but

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