During the intervals between trips this boat has been laid up and cared for at West Memphis, Ark., where the necessary repairs to keep her in serviceable condition have been made. The boat was docked and hull inspected at New Orleans April 23, 1910.

SURVEYS, GAUGES, AND OBSERVATIONS.

General survey of the Mississippi River.—This survey, authorized by the law creating the Mississippi River Commission to extend from the Head of the Passes near its mouth to its headwaters, has been made with a view of obtaining accurate data for topographical and hydrographical maps for use in study of the river in connection with planning improvements. The field work, comprising secondary triangulation, precise levels, topography, and hydrography, has been completed over the entire river, a distance of about 2,446 miles. The precise levels also extend down to the jetties, an additional distance of about 12 miles, to connect with the East Bay tide gauge. A summary of the survey to 1896 may be found in the Report of the Chief of Engineers for 1896, pages 3574 to 3576. The progress of the work since that date is given in the successive annual reports.

From the Passes to Keokuk, Iowa, the survey, in general, extends 1 to 2 miles back from the river on either side. From Keokuk to St. Paul, Minn., the survey usually extends back to the bluffs, and is at a few places as much as 8 miles wide. Above St. Paul and Minneapolis the topography was usually limited to 1 mile or less on either side of the river. In general, adjacent lakes have been included in the survey.

Resurveys. In order to ascertain what changes have occurred in the river below Cairo since the first general survey, the river has been resurveyed between its high-water banks, as follows: From Cairo to mouth of Arkansas River, 1902-1904; from Arkansas River to Vicksburg, 1894; from Vicksburg to New Orleans, 1895-1898; and from Forts St. Philip and Jackson, La., to the Head of the Passes in 1903-1904.

The results of the above resurveys from the mouth of the Arkansas River to New Orleans, and a comparison with the earlier surveys for that stretch of the river, have been published in the reports of the Chief of Engineers for 1896, pages 3577-3598, and 1897, pages 3672-3686. Those for the short stretch from the forts to the Head of the Passes were published in the supplement to Report of the Chief of Engineers for 1905, pages 41-45. Similar tables and diagrams of the elements of cross sections of the resurvey of 1902-1904, and of earlier surveys for comparison, of the stretch of the river from Cairo to the mouth of the Arkansas River, which have been in preparation in the drafting division for some time, are nearly completed, and a report thereon is being prepared.

Permanent marks.-Since the earlier surveys of the river a large number of the bench marks, which were intended to be permanent, have been disturbed or destroyed and many of them have caved into the river.

The systematic work of restoring old bench marks and establishing new ones was begun at Cairo in the fall of 1905. This work has been prosecuted during each low-water season since, and was completed to Donaldsonville, La., in January, 1910. The following is the work of this party during the last season in detail:

The party was organized early in October at Memphis and left that place on October 9, 1909, on the quarter boat Illinois in tow of the small steamer Mars with fuel barge. This party, in charge of Assistant Engineer A. T. Morrow, consisted of Junior Engineer E. J. Thomas, Surveyors F. A. Walton, E. B. Nettleton, W. H. Bainum, J. B. Moore, F. H. Wells, Recorder N. R. Sutton, 1 foreman, 7 survey men, 9 axmen, and boat's crew of 10 men, including pilot, steam engineer, stoker, deck hands, cooks, and waiters; making a total of 35 persons in the party.

Work was begun on October 18, 1909, at Greens Landing, 721 miles below Cairo, where the work of the previous season had closed, and was continued without interruption until January 15, 1910, when it was closed on secondary triangulation station North Base, about 2 miles below Donaldsonville, La., or 890 miles below Cairo.

A system of tertiary triangulation adjusted to the original secondary system was carried down the river for locating the survey marks. Base lines were measured on an average of one for every 15 triangles; a 200-foot steel tape, formerly used on secondary triangulation, was used for this work. Azimuth observations were made about every 20 triangles, except where it could be determined from the old secondary marks. Ordinary levels were carried down the

river connecting with the precise level bench marks, and all elevations are referred to mean Gulf level.

About 170 miles of river was covered during the season, 146 old bench marks were redetermined, 40 old secondary stations were connected with, 94 new marks were established, and 416 triangles in main system and 119 side triangles were closed.

About 75 per cent of the secondary triangulation stations connected with had subsurface marks only, consisting of glass bottles or earthenware jars which were uncovered by digging. Standard tile and pipe marks were placed at these stations, the original marks not being disturbed except in a few cases where they were not deep enough to admit of setting the new marks.

The bank and bar lines were determined over this stretch of the river and amounted to 399 miles.

At the conclusion of work at Donaldsonville the party disbanded. Assistant Engineer Morrow, with Surveyor Walton, returned with the tow to West Memphis. The outfit stopped at all the regular gauge stations between Donaldsonville and Memphis, except Mhoon Landing, and made a brief inspection, which mainly consisted of leveling to the gauge section in use at the time.

The total cost of the season's field work was $9,148.35, or $53.81 per mile of river.

After returning to the office Assistant Engineer Morrow, assisted by Surveyors F. A. Walton and E. B. Nettleton, began the reduction of the season's field notes. This work is now about 40 per cent completed.

The reduction of the previous season's field notes was completed in October, 1909.

Precise levels.-On account of certain discrepancies in the precise levels of earlier years on the lower river, the line was rerun from Baton Rouge, La., to the jetties in 1897-98. Since that time this work has been extended northward to Memphis, Tenn. The line from Biloxi, Miss., to New Orleans, La., has also been rerun. No field work was done during the season of 1909-10. It is the intention to relevel between Cairo and Memphis next season.

Reduction and plotting of the general survey.-The reduction and plotting of the field notes of the upper river survey, season of 1904, were completed, with the exception of a short strip just below Itasca Park.

Mapping.-Detail charts Nos. 252 to 261 above Minneapolis, Minn., scale 1:5000 were completed ready for publication.

Detail charts Nos. 262 to 267, of the same series, are well advanced toward completion.

The office force in the drawing division during the year consisted of Messrs. K. A. Widen, H. A. H. d'Ailly, C. R. Appiano, Paul Burgoldt, draftsmen, and Mr. C. W. Clark, assistant engineer in charge of this division.

Published maps and charts.—No maps or charts have been published during the year.

Maps and charts published by the Commission are as follows:

Map of the Lower Alluvial Valley of the Mississippi River from the vicinity of Cairo to the Gulf of Mexico in eight sheets, scale 1 inch : 5 miles, first published in 1887, and a third edition with additional data published in 1908.

Map of the valley of the Mississippi River from Cairo to St. Paul in four sheets, scale 1 inch: 5 miles, published in 1899.

District map of the Mississippi River from Cairo to the Gulf, showing the improvement and levee districts, in one sheet, scale 1 inch 5 miles, published in 1897.

Detail charts, 170 in number, scale 1: 20,000, and 4 index and 2 title sheets, showing hydrography of the river and adjacent topography, from the Gulf to Minneapolis, Minn., a distance of 1,957 miles.

Detail charts 1:10,000, otherwise similar to the above, from Minneapolis, Minn., to Lake Itasca, are in preparation and 51 sheets, extending from Minne apolis to above Leech Lake River, 1,265.5 miles above Cairo, have been published. Map of the Mississippi River, scale 1 inch 1 mile, in 77 sheets, from the Gulf of Mexico to 14 miles above Grand Rapids, Minn., 1,215 miles above Cairo; this series is to be extended up to the source of the river. A title page, index, and cover for the sheets below Cairo have also been printed.

Map of New Orleans and vicinity, in 4 sheets, showing Fort Chalmette, similar to the detail charts described above, but on a scale of 1: 10,000.

Map of Lake Itasca Basin, in colors, scale of 1:15,000, in 1 sheet.

Map of the St. Francis Basin, scale one-half inch to 1 mile, in 2 sheets. Re published in 1908 with additional data.

Gauges. The gauges in charge of this office comprise 38 regular gauges on the Mississippi River and its principal tributaries and 185 special high-water gauges on the Mississippi River between Cairo and the Head of the Passes. Also two automatic tide gauges on the Gulf of Mexico, one at Biloxi, Miss., and one at East Bay, La. A detailed description of these gauges is printed in the supplement to Report of the Chief of Engineers, U. S. Army, for 1902, pages 52 to 59.

All of the regular gauges were inspected and repaired during the last lowwater season with the exception of that at Cape Girardeau, Mo. Owing to the limited amount of funds available this year for the Commission gauges, only urgent repairs were made to these gauges and the low-water inspection trip on the main river was made as brief as possible.

The high-water gauges below Cairo were known to be in fair condition generally, and except in a few cases where the observers had reported the gauge disturbed, were not inspected. Some inexpensive float gauges were made, having a simple device to fix the float at the maximum stage. Seven of these experimental gauges were set at the sites of as many high-water gauges between Mhoon Landing, Miss., and Natchez, Miss., for the purpose of a practical test; the results will be known after the next inspection.

As there has been practically no high water so far this year, the high-water inspection of the gauges on the main river below Cairo was not begun until May 12. It is expected that the mid-sections of the gauges can be inspected on this trip and left in good condition for the summer. The following is the work in detail:

The low-water inspection of all the regular gauges on the Mississippi River from Memphis, Tenn., to Fort Jackson, La., the gauge at Barbre Landing and the tide gauge at East Bay, La., was made by the party on the U. S. steamer Patrol, in charge of Junior Engineer T. B. Perry, with Surveyors R. A. Brown and E. L. Perry and crew. The steamer left Memphis on October 14, 1909, and returned on November 27, 1909, and was laid up at West Memphis.

The severe storm from the Gulf in September, 1909, had disturbed many of the gauges on the lower river, and at the inspection the following large errors were found in the disturbed sections: Red River Landing, La., gauge was 2.2 feet high; Bayou Sara, La., gauge was 0.7 foot low; Donaldsonville, La., gauge was 2.3 feet low.

Some of the gauges above the influence of the Gulf storm had also been disturbed from various causes, the larger errors being as follows: Helena, Ark., gauge 2.1 feet low, disturbed by transfer boat; Sunflower Landing, Miss., 0.9 foot low, sliding bank; Arkansas City, Ark., 0.9 foot high, knocked by logs and rafts. Errors found in gauge sections at other stations were generally less than two or three tenths foot. All of the disturbed sections were rebuilt correctly. All the gauges were tested by duplicate lines of ordinary levels from the permanent bench marks at the respective stations. New steel bulletin frames of the latest type were erected at Greenville, Miss., and Sunflower Landing, Miss. The bulletins at the other stations were repainted where necessary and left in fair condition.

Nine of the high-water gauges were visited and repaired and two new highwater gauge observers were appointed. One of the experimental float gauges was set at each of the following high-water gauges: Nos. 64, 67, 81, 82, 88, 102, and 132.

After laying up the Patrol at West Memphis Junior Engineer Perry inspected and repaired the regular gauges on the Mississippi River at Cottonwood Point, Mo., New Madrid, Mo., Columbus, Ky., and Cairo, Ill., using the small steamboats engaged on bar surveys for the purpose. This work was completed at Cairo on December 3, 1909.

The regular gauge at Fulton, Tenn., was inspected and repaired during the low water by Surveyor J. H. Opp, on the small steamer Vulcan.

All the gauges on the tributaries were inspected during the low water of 1909, as follows: On the Ohio River at Louisville, Ky., August 6; on the Tennessee River at Florence, Ala., November 4; on the Cumberland River at Nashville, Tenn., November 5, by Assistant Engineer Kivas Tully. On the Red River at Shreveport, La., November 3; at Alexandria, La., November 4; and at Fulton, Ark., November 26; on the Arkansas River at Little Rock, Ark., November 27; on the White River at Clarendon, Ark., November 24; and at Jacksonport, Ark., November 28, by Surveyor R. A. Brown. On the St. Francis River at the Iron Mountain railroad bridge, November 29, by Surveyor E. L. Perry. These gauges

were repaired and both gauges and bulletin frames were repainted where necessary and kept in good condition.

The regular gauge on the Mississippi River at St. Louis, Mo., was inspected by Surveyor F. E. Early, and a temporary section reading from zero to 5 feet was set on December 23, 1909.

On the night of January 13, 1910, the river rose suddenly from 27 feet to 31.9 feet on the gauge, and as suddenly fell again. This was due to the breaking of an ice gorge in the Missouri River and caused great damage to floating property on the river front at St. Louis. Two barges were stranded on the levee at the site of the inclined gauge, and it was necessary to set a temporary gauge to obtain the readings until the river fell below the barges. This gauge and its bench marks were connected with permanent bench mark 15 on the Eads Bridge by a duplicate line of precise levels on January 28, 1910, by Junior Engineer E. J. Thomas. The results indicate a slight settlement in the gauge benchmark on the elevated railway strut, but no change in the steel-concrete inclined gauge.

Five steel bulletins for displaying the gauge readings to boats passing the gauge stations were made under contract by the Henry Vogt Machine Company, of Louisville, Ky. These are of the same type shown on plate 3 of the annual report of the Mississippi River Commission for 1903, following page 68 of supplement to report of Chief of Engineers. The only change made this year was to have blank plates attached to the land side of the plate frames, so that the reverse side of the figured plates are not visible.

The usual office work tabulating and plotting the gauge records has been performed and corrections for errors in gauges as deduced from the inspectors' level notes or from coordinate plots have been applied.

The hourly ordinates of the tide gauges at Biloxi, Miss., and East Bay, La., have been scaled off the tide sheets and tabulated.

The highest and lowest gauge readings, Mississippi River and tributaries, for 1909 and the extreme readings prior to 1909 are given in Table No. 1.

The hydrographs of the daily readings of all the regular gauges on the Missis sippi River from Cairo, Ill., to Fort Jackson, La., June 1, 1909, to May 31, 1910, are given on plate No. 1.

The annual pamphlet of river stages for the year 1909 has been prepared and the printing is nearly completed. This pamphlet contains the records of 67 gauges and comprises about 152 pages.

The annual hydrographs of the Mississippi River and tributaries for 1909 have been prepared in four sheets and blueprints issued.

The Mississippi River did not reach the stages prescribed for slope observations during either high or low water periods during the year, and therefore no observations were made except on the regular gauges.

Discharge observations.-The Mississippi River reached the stage prescribed for high-water discharge observations at St. Louis, Mo., and Thebes, Ill., in July, 1909.

The discharge at St. Louis was measured by a party in charge of Junior Engineer E. J. Thomas, with Surveyors J. G. Frost, W. W. Primm, and E. De Lorme, on the U. S. tender No. 4, loaned by the St. Louis engineer district, from July 12 to 20, 1909.

The discharge at Thebes was measured from July 14 to 21 by a party in charge of Junior Engineer T. B. Perry, with Surveyors R. A. Brown and C. W. Schweizer, on the U. S. tender No. 8, also loaned by the St. Louis engineer district. These observations were reduced and the results tabulated in the office. No other discharge observations have been made during the period covered by this report.

The reduction of the high-water discharge observations of 1909, in progress at the date of my last report, was completed and the results tabulated. These comprise observations on the Mississippi River at Columbus, Ky., Helena, Ark., Arkansas City, Ark., Vicksburg, Miss., Red River Landing, La., Carrollton, La.: on the Atchafalaya at Simmesport, on the Black River at Jonesville, and on the St. Francis River near its mouth.

Eleven velocity meters used in discharge observations were rated at the settling basins of the St. Louis waterworks at Bissels Point, January 21 to 27, 1910.

The scientific records, maps, and construction drawings of the Secretary's office have been catalogued es received and the card indexes kept up. Various requests for information and data of the Mississippi River have been complied with.