which had not been connected at time of running the precise line on account of their distance from it; nor had any connection by wye levels been run at time stone line was put in, as the bench marks of 1880 and 1881 from which the stone lines were established were found to be unreliable. The party left St. Louis, September 23, for Crescent, Iowa, the farthest point at which work was required. The party consisted of an assistant engineer and two rodmen, and such additional force as was required was employed where necessary. This was done to save transportation. Work was begun on September 25 and continued until November 3, when work was completed at Boonville, Mo. As stone lines 48-41, inclusive, had been leveled in one direction, they were considered unreliable and it was thought best to rerun them. Assistant Engineer L. P. Butler reported at Glasgow, Mo., October 25, to assist in rerunning these lines, as the river crossings could be made much better by two parties than by one. With but two exceptions these isolated stone lines and benches were connected with precise bench marks, and in these cases, connection was made to benches that were reliable. No very large discrepancies were found, except on stone line No. 101, where an error of nearly 2 feet was discovered. There were several discrepancies of from 1 to 0.2 of a foot. All stone lines and bench marks that were doubtful were rerun or good connection made to reliable benches. There were 70 miles of checked levels run and 8 river crossings made. Party was out forty-two days, including time in going from St. Louis to the field and in returning. The total cost of survey, including transportation and expressage of instruments, was $719.90, or $10.28 per mile of checked levels. The cost per mile, exclusive of transportation and expressage of instruments, was $8.35. Bench mark No. has been washed out by the river; No. could not be found, 77 45 2 and was said to have been covered by driftwood and deposits of sand. Since returning from the field the notes have been checked and the new values of bench marks tabulated. The field notes of precise level survey of May and June have been reduced and checked, descriptions of bench marks have been written up, and all are now in form for publication. No errors were found in the field notes, and all lines check within the precise limit. The probable error per kilometer for the whole line is 0.67 mm. The precise leveling rods X and XIII have been compared with the standard meter of Mississippi River Commission and found to be of normal length. These rods were compared in April, 1863, by Assistant Engineer O. W. Ferguson, and found to have been long, but as they had just returned from a field season near the gulf, no weight was given to that comparison. For my report on field operations see Appendix A 7 of report of Missouri River Commission for 1893. On account of so many large discrepancies being found between the precise levels and the ordinary levels, two of which proved on examination to be errors of computation, it was decided to recompute the level notes over stone lines from the mouth of river to Sioux City, Iowa, and from Fort Benton to Three Forks, Mont. The large discrepancies between the precise and the ordinary levels were found to be due (1) to errors in the field notes, lines not checking and this fact not being discovered; or (2) to errors of computation; or (3) to stone lines having been put in from old bench marks which either were not identified or were in error. Quite a number of small changes were made from the former reduction. The clevations of the bench marks as reduced depend on precise bench marks, generally not more than 3 or 4 miles distant; so no large discrepancy may be expected. The level notes between Fort Benton and Three Forks, Mont., were recomputed and a correction of+13.522 feet was applied to elevation of B. M. 4, at Fort Benton. This elevation of B. M. was brought down from Northern Pacific Railroad levels at Gallatin, Mont., by Assistant Engineer G. A. Marr in 1890. The correction of+13.522 feet depends on elevation of B. M. 4, at Fort Benton, as determined from the precise benches of Missouri River Commission at Sioux City, Iowa, by survey parties under Capts. C. F. Powell and H. F. Hodges and the Missouri River Commission. A book of bench marks is now being prepared and is nearly completed. This book will contain (1) all bench marks of 1881 and 1882, also those of former surveys that were connected with at that time; (2) all bench marks of stone lines put in from 1884 to 1890; (3) all precise bench marks of 1887, 1892, and 1893 also all precise temporary bench marks that were considered sufficiently permanent for future use. It is proposed to designate the degree of accuracy of these bench marks by names and by the use of large and small type. The bench marks included in this book are from mouth of river to Sioux City, Iowa, and from Fort Benton, Mont., to Three Forks, Mont. The precise bench marks from Sioux City, Iowa, to St. Joseph, Mo., have been platted on the detail maps, scale 1 inch =1,000 feet. At time of running precise line accurate stadia distances were taken to located points of topography, and as line of levels was along the railroad the bench marks have been platted on the detail sheets with about the same degree of accuracy as that of the adjacent topography. Summary of work done by Assistant Engineer O. W. Ferguson: The remaining work on field notes that was unfinished at end of fiscal year 1893 was completed. The precise and temporary precise bench marks were platted on detail sheets, scale 1 inch 1,000 feet, from St. Joe to mouth of river. Several profile sheets were made in office: One showing the discrepancies between the Missouri River Commission preciselevel line and the bench marks connected with by precise-level party from St. Joe to mouth of river; A second showing discrepancies between direct and reverse precise level line, from St. Joe to mouth of river; A third showing discrepancies between U. S. Coast and Geodetic Survey and Missouri River Commission's precise levels from Kansas City to St. Louis; and A fourth showing limit of error of closure between precise-level lines over same stretch. The following is a summary of work of Y level survey under my charge: DESCRIPTIONS AND ELEVATIONS OF PRECISE LEVEL BENCH MARKS OF SPECIAL All elevations are given in both meters and feet, and refer to St. Louis City directrix as zero. The elevation of this above Biloxi sea level is 412.731 feet. A P. B. M. is a precise bench mark that is set to be practically permanent. All P. B. Ms., excepting 327 B, which is a cross on B. M. stone, are (1) top of copper bolts in regulation B. M. stone, or (2) center of copper bolt set horizontally, or (3) marks on bridge piers. The value of the meter used is 3.2808693 feet. Descriptions and elevations of precise level bench marks, etc.-Continued. Elevation. Number. Description. Meters. Feet. P. B. M. 360 C=137. Gauge B. M., Blair, P. B. M. 336137. Top of cap, P. B. M. 336-117. P. B. M. 336 A= 147. Top of cap, P. B. M. P. B. M. 336 B = 12, Top of cap, P. B. M. Top of cap, P. B. M. 327. P. B. M. 327 A. Top of cap, P. B. M. 327 A. P. B. M. 327 B, Nebraska City, Nebr. Gauge B. M., Nebraska City, Nebr. P. B. M. 318 = 106, Top of cap, P. B. M. 318-19. P. B. M. 318 A=109. Top of cap, P. B. M. 318 A 199. P. B. M. 318 B=106. Top of cap, P. B. M. Is on west pier of railroad bridge across Missouri River, Is on west pier of railroad bridge across Missouri River, Is about 14 miles east of railroad bridge across Missouri On top of stone foundation of north end of first iron bent Is at railroad bridge across Missouri River at Plattsmouth, Is 3,884 feet northward from depot at Nebraska City Is about 18 miles west of Nebraska City Junction, Iowa, Is in west abutment of Burlington and Missouri River R. Is on west abutment of Burlington and Missouri River R. Is at Phelps, Atchison County, Mo., in the northeast Is about 1 mile west from Phelps, Mo., on south side of Is at Brownville, Nebr., at northwest corner of Main Is 627 feet southward from the depot at Napier, Holt Descriptions and elevations of precise level bench marks, etc.—Continued. 228= P. B. M. 228 A. P. B. M. 228 B= Is about 650 feet east of the depot at Fortescue, Mo., 59 Is about 10,830 feet west from Fortescue, Mo., 66 feet north Is 7,600 feet east from east pier of Burlington and Missouri Is in west pier of Burlington and Missouri River R. R. Ο B. M. Is in west face of a granite block in the west side of the Is at Rulo, Nebr., in dooryard of John Stull, at west side Is on right bank about 3 miles below Hannibal and St. Is on west end of north pier of Chicago, Milwaukee and ... Is on left bank 970 feet above Chicago, Milwaukee and Top of cap, P. B. M. Top of cap, P. M. B. 171-52. P. B. M. 171 A. = Is opposite De Witt, Mo., on line running east and west .. Is on right bank, opposite De Witt, Mo., and about one-half 134.5626 441.482 135.8033 445.553 132.4888 434. 678 Descriptions and elevations of precise level bench marks, etc.—Continued. TABULATION OF PRECISE LEVEL RESULTS, BLAIR, NEBR., TO DE WITT, MO., 1893. In the table of results column 1 gives the bench mark, T. B. M., signifying temporary bench mark, and P. B. M, signifying precise level bench mark. Column 2 gives the bench mark from which that in column 1 was determined. Column 3 gives the length of stretch in meters. Column 4 gives the distance in kilometers from initial bench mark. Column 5 gives the direction in which the line was leveled. Dir. is for the direct line. Rev. is for the reverse line. Column 6 gives successive differences of elevation in millimeters between bench marks and the means of such determinations. Column 7 gives the residuals found by substracting each determination from the mean. Column 8 gives the discrepancy between the direct line and the mean, and is the algebraic sum of the residuals. Column 9 gives the discrepancy between the reverse line and the mean, and is the algebraic sum of the residuals. Column 10 gives the probable error, r, of the mean in column 5. Column 11 gives the probable error, R, of the mean elevation of each bench mark as computed from the beginning of the section. Column 12 gives the total rod correction as computed from initial bench mark (not used). Column 13 gives the elevation in meters of all bench marks referred to St. Louis directrix. Column 14 gives the elevation in feet of all bench marks referred to St. Louis directrix. Column 15 gives the elevation in feet of all old bench marks connected with referred to St. Louis directrix. Column 16 gives the discrepancy in feet of old bench marks. Column 17 gives the initial of observers; T. is for Assistant Engineer O. H. B. Turner. Bench marks marked with an asterisk (*) are not in the main line. |