Page images
PDF
EPUB

there are distinct differences in the rates of travel through different reaches down to Red River Landing. These differences in the travel have as yet not been connected with any physical cause, and beyond the supposition that they depend in some way on the relative lengths of pools and bars, possibly combined with slope and mean depth, there is no explanation for them,

The curve of interval to distance from Cairo is shown plotted on Pl. VII, and presents more clearly to the eye these irregularities of travel. On this plate, following out the original assumption that the interval was determined to within 40.05 of a day, dotted lines have been drawn above and below the curve, diverging by this amount for each full reach. They represent on this assumption the extreme possible error of the total interval from Cairo down to any point. The possible error of interval between intermediate points is of course less, and can easily be made up by this allowance of 0.05 of a day for each full reach, or any part of a full reach; for while 0.05 is taken as the limiting error, say, from Cairo to Helena, it is also taken as the error from Cairo to New Madrid, or any other part of this Cairo-Helena reach, which was studied as a whole.

The limiting gauges to the full reaches are marked with an asterisk on Pl. vII; also on the plate the curves of limiting error have not been extended below Red River Landing since, as before considered, the determinations of the intervals there may not be so exact.

In the annual report of the Mississippi River Commission for 1890 there is a tabulation giving in long reaches the mean water area from Cairo down for the bank full stage. (See Report of Chief of Engineers, 1890, page 3129.)

From this, by taking the discharge for this stage as 1,000,000 cubic feet per secV ond, we may determine approximately the mean velocity of these reaches, or for R the bank full stage from Cairo to Carrollton. This is given in Tabulation II, in comparison with the velocity of flood travel for the same reaches, deduced from the time intervals.

[blocks in formation]

* The reaches in the Commission's report. New Madrid to Plum Point and Helena to Arkansas River, are respectively taken as New Madrid to Fulton and Helena to Arkansas City to correspond with reaches for which the intervals have been determined.

If the deduced mean velocities of the reaches are to be relied on, there seems to be no definite connection between this and the flood travel; and beyond the further evidence that the travel of floods below Baton Rouge is altogether out of the range of a velocity movement, there is little to be gained from this comparison.

It should, however, be stated that while there are marked differences in the reaches, the mean values down to Red River Landing of the flood travel and of the mean velocity are very close together; the mean flood travel being 5.03 and the mean of the mean velocities at the bank-full stage being 4.96 per second.

It is thought that this may be simply a coincidence, or it may point to a general tendency towards flood travel above Red River Landing as an average being developed, so as to have the general mean velocity of the bank-full stage. This might either mean perfect circulation at stages whose averages for the whole river correspond to the mean velocity of the bank-full stage, or might as well mean the disappearance of the transmission element of the flood's motion at these stages.

But whatever uncertainty there may be in the theoretical consideration of the causes of this law of flood movement, I think we may safely say that there is in hy

draulics no law which more accurately expresses so broad a generalization of observed facts and whose field of application gives so great a promise in the study of the flow of water in natural channels.

Very respectfully, your obedient servant,

Lieut. Col. CHAS. R. SUTER,

Corps of Engineers, U. S. A.

APPENDIX 3.

JAMES A. SEDDON.
Assistant Engineer.

REPORT OF CAPTAIN S. W. ROESSLER, CORPS OF ENGINEERS, UPON SURVEY OF NONCONNAH ROCKS.

UNITED STATES ENGINEER OFFICE,
Memphis, Tenn., May 24, 1892.

SIR: I have the honor to submit herewith the map of a survey of Nonconnah Rocks made pursuant to a resolution of the Commission dated November 18, 1890. The survey included soundings in the vicinity of the rock, examination by a submarine diver and the obtaining of specimens of the stone.

The rock is located about 5 miles below the city of Memphis, opposite and above the mouth of Nonconnah Creek, and is about 700 feet out from the Tennessee shore and 2,000 feet from Presidents Island shore.

A previous examination of the rock was made by Capt, Leach, September 19 and 20, 1889, and a report made by him under date of December 13, 1889. At that time the main channel was between the rock and Presidents Island, and a narrow channel, rarely used, existed between the rock and the Tennessee shore. Around the rock and partly covering it was a large flat gravel bar, sloping upwards toward the rock where the general level of the bottom was about 1 foot below the water surface, corresponding to zero on the Memphis gauge. Since that survey the channel has moved from Presidents Island to the Tennessee shore and there has been a deep scour in the gravel bar in the vicinity of the rock, on all sides of it, and in the channel between it and the Tennessee shore. About 150 feet east of the rock the scour was about 27 feet, and 200 feet farther in the same direction, 16 feet; 200 feet above the rock, 10 feet; 350 feet west of the rock toward Presidents Island shore, 4 feet, and in the immediate vicinity of the rock, the scour varied 17 to 27 feet. The rock itself shows the effect of erosion in the interval, the height at the last survey (2.80 above zero stage) being 3 feet below that indicated by the survey of 1889.

The section of the rock by a horizontal plane 8 feet below zero stage has approximately the shape of an ellipse with longer and shorter diameters respectively 190 and 130 feet. Above this section, the shape of the rock, as well as can be inferred from the soundings taken, is something like an obliqué frustum of a cone with a steep slant on its east side and a flat slope on the opposite side toward Presidents Island, and contains approximately 3,000 cubic yards.

Since the change in the position of the channel to the Tennessee shore, the rock has become a more serious obstruction to navigation than it had been theretofore, and its removal made more urgent.

It is difficult to estimate the cost of excavating it. The material is a soft, ferruginous sandstone or pudding stone easily broken up and pulverized under a hammer, which would be pulverized to a large extent by blasting and washed away by the current. A large part of the highest projection at the eastern end of the ledge can also be blasted off into deep water, thus reducing materially the amount that would have to be dredged up and towed away.

In the absence of any similar work as basis for an estimate, I place the cost at $2 per cubic yard, or $6,000 for excavating the rock to a depth of 8 feet below zero stage. The method of removal proposed is to do the work at low water, to break the rock by surface blasting, to proportion the size of blasts so as to pulverize the rock as much as possible and remove by dredging the coarser material which the current will not move.

It is proper to add that the difference between my estimate and Capt. Leach's of the quantity of rock to be removed, mine being less than one-half of his, is due to the fact that a larger part of the rock at the time of his examination was covered by the gravel bar, a portion of which, since scoured away, was probably included in his estimate as rock.

Very respectfully, your obedient servant,

Gen. C. B. COMSTOCK,

President Mississippi River Commission.

ENG 92

-183

S. W. ROESSLER,
Captain of Engineers.

APPENDIX 4.

REPORT OF CAPTAIN CARL F. PALFREY, CORPS OF ENGINEERS, SECRETARY MISSISSIPPI RIVER COMMISSION.

UNITED STATES ENGINEER OFFICE,

St. Louis, Mo., May 31, 1892.

GENERAL: I have the honor to present the following report of operations under my charge as secretary Mississippi River Commission and assistant to construction committee from July 1, 1891, to May 31, 1892.

These works are carried on under the following allotments from the appropriations approved September 19, 1890, and March 3, 1891, made by the Commission and approved by the honorable the Secretary of War:

First. "6 Mississippi River Commission," applicable to salaries of three Commissioners, to expenses of offices of president and secretary, and to expenses of meetings and inspections of Commission.

Second. 66 Surveys, gauges, and observations," applicable to the general survey of the river, to collection and office reduction of physical data, and to general examinations and computations not confined to any one district.

Third. "General service," applicable to supply of stone, maintenance of plant, and general aid to works in the districts.

The small balances from earlier appropriations which appear in the financial statement are set off by outstanding liabilities for telegrams, which can not, under existing orders, be adjusted.

MISSISSIPPI RIVER COMMISSION.

The Commission has held three sessions during the period reported, at New York City, July 15-17, 1891; from St. Louis to New Orleans, November 5-18, 1891; from St. Louis to New Orleans, May 4-10, 1892.

SURVEYS, GAUGES, AND OBSERVATIONS.

Secondary triangulation.—On July 1, 1891, a party, in the field since April 25, under Assistant Engineer Charles W. Stewart, with Assistant Engineers F. B. Maltby, A. T. Morrow, and George H. French, under his orders, had carried their work 4 miles above Burlington, Iowa, having then covered about 50 miles of river, occupied 31 stations, marked 34 triangulation points, and 19 stone lines. This party completed its field work on July 28, at Port Louisa, Iowa, covering during the season about 85 miles of river. Reconnoissance had been made for more triangulation, but the progress of this work was slower than had been anticipated, owing in part to hazy weather, and in part to the great number of stations found necessary in the narrower parts of the valley. From Keokuk to Lomax, a distance of 36 miles, there were 25 triangles, sides averaging 2.3 miles; from Lomax to Port Louisa, a distance of 49 miles, there were 13 triangles, sides averaging 7.3 miles; 24 stone lines, Nos. 112 to 135, inclusive, have been marked by 81 tile and pipe monuments. A base line nearly 34 miles long was measured along the railroad track near New Boston, Ill.; observations for azimuth made at "West Base." At the close of the field work, Assistant Engineer Stewart returned to the office for computation and reduction of the triangulation; the instructions for this work are given in Annual Report for 1891, pages 3474-3476.

The chain consists of 49 triangles, extending from base line measured at Keokuk in 1881 to base line at New Boston; its length along its axis is about 78 miles. The greatest error in closing any triangles is 05.03; the least, 00.08; the mean of all 02.33.

The base line was measured in two sections. The first section, about 2,500 meters, was measured east and west in good weather; discrepancy of two measurements, 1:575,346. The second section was measured east and west, the sun coming out during measurement east; discrepancy, 1:171,390. A second measurement east was taken, giving with measurement west a discrepancy of 1:4,063,050. These results were accepted. The measured length of base line is 5,506 meters; the length, computed from base at Keokuk, is 5,506.2576 meters; discrepancy, 1:21,374. The observed azimuth of base is 253° 18′ 49.06; the azimuth computed from Keokuk base is 253° 18′ 48.48; discrepancy, 00.58.

The location of stone-line monument has been determined by direct observation from triangulation stations with triangulation instruments, or by short lines of connection run with Gambey transit reading to 5". The error of position is well within the possibility of delineation on a scale 1: 10,000.

Detailed report of this work by Assistant Engineer Stewart, with tabulated results, is appended (marked A).

On March 28, 1892, Assistant Engineers Stewart and French took the field near Muscatine, Iowa, for reconnoissance and location of triangulation stations from Port Louisa, Iowa, northward. This reconnoissance was carried to Dubuque, Iowa, and base lines selected near Rock Island and Dubuque.

The full party, consisting of Assistant Engineer Stewart, in charge, Assistant Engineers Morrow and French, Recorders C. L. Ockerson, O. N. Axtell, and M. I. Powers, and crew and working party, consisting of T. C. Hockridge, master and foreman, and twenty-three men, assembled on board steamer Patrol at New Boston, Ill., on Ápril 25, and began work at Port Louisa, Iowa, on April 26.

On May 31, this party had reached Fairport, Iowa, having occupied 16 triangulation stations, marked 18 triangulation points and 12 stone lines, the completed work covering about 22 miles of river. It has rained on 27 days in May.

Precise levels.-On July 1, 1891, a double precise-level party, under Assistant Engineer O. W. Ferguson with Assistant Engineer A. L. Johnson, working from St. Paul to Savanna, Ill. (in the field since April 25), was at Alma, Wis., having run 95 miles by river, and placed 48 permanent bench marks; a single precise-level party under Assistant Engineer James A. Paige, working from Duluth to St. Paul (in the held since April 26), was near Willow River, Minn., having run 54 miles and placed 12 permanent bench marks.

The field work of the line from St. Paul to Savanna was completed October 20, connecting with work of 1883 at three bench marks. The length of this line is 301.2 miles; 379 permanent bench marks were placed; 106 of tile and pipe; 57 of copper bolts; 216 cut in rock in situ or on trees; 49 bench marks of former United States Engineer surveys were connected and also 12 gauges and 7 city bench marks.

The line of this party was in general over favorable ground. About 84 per cent was on railroads; about 16 per cent along river; there were six river crossings. The party was quartered and subsisted on quarter boat Kentucky, moving downstream by aid of the current, and never far from the work.

The field work of the line from Duluth to St. Paul was completed on September 28. Connection was made on September 26 with bench marks 68, 69, and 71 of the St. Paul-Savanna line; about 3 miles of the line was rerun after this connection. The length of this line is 156.2 miles. Forty-two permanent bench marks were placed; 32 of tile and pipe; 10 cut in rock in situ or on trees. Three engineer bench marks at Duluth and the engineer gauge there were connected.

The line of this party was over ground less favorable than that of the other. About 12 per cent was on wagon roads, rough, and with abrupt changes of line, the remainder on railroad track. Departures from the railroad to save length of line proved disadvantageous. The rerunning of 3 miles was owing to one of these. The party was furnished with wagon transportation but not with camp outfit, depending for lodging and subsistence upon villages and farm houses. In thinly-settled parts of the line this caused an important loss of time. Even in well-settled districts, the hours at which work of this kind is best done made it desirable that the serving of meals be under the full control of the chief of party,

The preliminary instructions for this work are given in Annual Report for 1891, pages 3476-3480. Instructions changing the order of reading the rods were, by direc tion of the president Mississippi River Commission, given after work had begun. They were repeated in the subreports.

The chiefs of party made each the reduction of his own line. The results are as follows:

[blocks in formation]

Detailed reports, with tabulated results, and descriptions of bench marks are appended as follows: St. Paul-Savanna line, by Assistant Engineer Ferguson, (marked "B"). Duluth-St. Paul line, by Assistant Engineer Paige (marked "C"). Topography and hydrography.—On August 4, a party under Assistant Engineer F. B. Maltby, with Assistant Engineers A T. Morrow (on tertiary triangulation and stone-lines), W. G. Comber, G. H. French, O. W. Connet, E. J. Thomas, and H. Dunnaway (on topography), E. L. Harman (on hydrography and later on topography), and recorders L. D. Cabanné, O. N. Axtell, C. L. Ockerson, and M. I. Powers, with T. C. Hockridge, master of boat (later on hydrography) and crew and working party of one pilot, one engineer, and forty to forty-five men, began work at Stone-line 61, near Alton, the close of work of 1889. Their work for the season was closed at Stone

line 94, near railway bridge at Hannibal, Mo., a distance of about 118 miles by river. Outside the limits of detailed work, bluff-lines were located on right bank from St. Charles to Clarksville, Mo., about 50 miles, on left bank near Hamburg Bay, about 40 miles, and along both banks of Illinois River for about 10 miles; also water courses and lakes between the belt of detailed work and the bluffs. The stage of the river was exceptionally low, and very full detail of bars and islands was obtained. Very little field-work time was lost by rain.

The party was quartered and subsisted on steamer Patrol and quarter boat Illinois, kept as nearly abreast of the work as practicable.

The instructions for this work are given in Annual Report for 1891, pages 3481-3485. The tertiary triangulation occupied 236 stations, and closed on three measured bases and seven sides of secondary triangulation; average error of closing, 1:4870. Thirty-three stone-lines were marked.

The stadia lines, aggregating about 325 miles, were checked by 165 closings upon determined points, and by 115 azimuths; average error of length at closing, 1:875, of azimuth, 02.4.

Lines of ordinary levels on both banks, with crossings near each stone-line, checked each other with a greatest discrepancy of 0.203 feet, average of 0.101 feet. These lines were checked at 22 points upon lines of precise levels run in 1880-'81, with discrepancies ranging from +0.147 to −0.135. Seventeen high-water marks of dates from 1851 to 1888, whose history and accuracy appeared well established, were connected.

Soundings were taken on 853 sections, also in continuous line where channel was evident, and in several trial lines over shallows and divided channels. These lines were useful to pilots during low water, developing in some cases better channels than those in use, and in one revealing an important obstruction, which was buoyed and reported to the light-house inspector.

Field platting was little done except the closing of instrumental lines; the field notes are full and carefully kept.

Detailed report of Assistant Engineer Maltby is appended (marked D).

Caving banks and stone-lines.-In accordance with resolutions of the Commission, of· November 19 and 24, 1891, and March 22, 1892, a party was sent out to examine the condition of permanent marks of the Commission's surveys below Cairo and to determine the amount of caving since the original surveys, the interval varying for different parts of the river, being, on the average, about 10 years.

The party, consisting of Assistant Engineer F. B. Maltby, in charge, with Messrs. French, Thomas, Hockridge, and Ockerson, left St. Louis on the Patrol, on November 17, and began work at Cairo on November 20.

On January 1, 1892, at 6 a. m., the Patrol, moored against the left bank near Commerce, Miss., was struck by a sudden and severe storm. Her stern line parted, and she swung out into the stream. The action of wind and current careened her till the lee side of boiler deck was under water, and she sank with bow against the bank, and stern in 13 feet of water. The pilot and working crew on main deck were up; the survey party on boiler deck were still in bed, and escaped with much difficulty and little clothing, in a temperature below freezing. One of the deck crew, Parke Driscoll, was lost; the body not recovered. All of the deck crew lost clothing and other personal effects. The boilers were displaced by the shock, and stoves and heavy furniture thrown down. The instruments and records were saved with no material injury.

The steamer Pete Kirns was supplied in place of the Patrol by the officers in charge of the first and second districts. The party was transferred to her and work was resumed on January 8. Assistant Engineer Maltby resigned charge of the party, and Assistant Engineer A. T. Morrow relieved him on January 16. In his hands the work was carried on, reaching Donaldsonville, La., on March 22. Here about half of the party was discharged. On the return trip certain bench marks which had been covered by snow when passed in the survey were searched for, and new descriptions of bench marks were prepared where needed.

The nature of this work did not admit of detailed instructions. For the balance of his two works, and as a reasonable time-limit on the search for marks, the chief was directed to push his bank-line survey so as to complete it in one low-water season; not to delay his whole party for the marks of any stone-line after two had been recovered, and not to delay more than a day for any stone-line if the one before it was fully established. Some gaps in the series, left under this instruction, were filled on the return trip.

Sheets of tracing linen with protractors printed on them were supplied. The projection and permanent marks connected with, were traced on these from the charts, scale 1:20000, and the shore line platted on same scale. These plats were sent in at intervals of ten days, or when mail communication was had. The results were transferred at once in the office to the 1:20000 charts and reduced on the inch-mile maps. The caved areas were shaded with lead pencil, the levee lines as received from the

« PreviousContinue »