Lawrence Bradford, draughtsman, from the scale of the original map of 200 feet to the inch to a scale of 1: 5000. 2. Tracing copy of survey of Lynn Harbor, scale of 1: 5000, made in May and June, 1883, under directions of Maj. Charles W. Raymond, Corps of Engineers, by party in charge of H. F. Bothfeld, assistant engineer, aided by Lawrence Bradford, draughts man. 3. Tracing copy of "comparative profiles" on gauge lines I to VI of maps of surveys of 1866 and 1883. 4. Tracing copy of drawing illustrating rise and fall of tides during one lunation. 5. Tabular statements: No. 1. Rise and fall of tide during one lunation, average for each hour of flood and ebb. No. 2. Area and tidal body (comparative) from surveys of 1866 and 1883. No. 3. Distribution of tide-water, for each hour of flood and ebb, in Lynn No. 4. Distribution of tide-water at certain periods of flood and ebb in Lynn No. 5. Current observations made in June, 1883. No. 6. Simultaneous tide observations at tide-staffs at Black Rock Wharf, As these drawings and tabular statements are believed to contain most of the information desired by the Board of Engineers, I shall limit myself in this report to a few remarks in reference to the character and general result of the survey of 1883, and in relation to its present and former condition, and give any information derived by inquiry of responsible persons. SURVEYS OF LYNN HARBOR. 1. Survey of 1866 (A. Boschke's).-The United States Coast Survey having indorsed A. Boschke's survey of Boston Harbor, I could not hesitate to consider the map of his survey of Lynn Harbor in 1866, notwithstanding that no mention was made thereon of the plane of reference to which the soundings had been referred, as being in the main a correct representation of the condition of Lynn Harbor at that time. By close investigation it was ascertained that the United States Coast Survey benchmark on Boston Light-house Island had been used for establishing mean high and low water reference for Lynn Harbor, but to make quite sure of that fact the United States Coast Survey Office at Washington was requested to furnish a copy of the tide observations known to have been taken at the Charlestown navy-yard during the time of A. Boschke's survey of Lynn Harbor. From these observations I found that the soundings on the map of A. Boschke's survey had been referred to the plane of mean low water, which, from the tide observations, taken during one lunation in 1883, was found to be one-tenth of a foot below that determined for the recent survey. The tracing submitted herewith is a correct copy at a reduced scale of 1 to 5,000 of A. Boschke's map of the survey of 1866; it also shows, besides Lynn Harbor proper, the lower part of the Saugus River as far up as to where the Eastern Railroad Bridge crosses it, and the largest part of Chelsea Creek. This survey was principally made for the purpose of establishing harbor lines and for preparing a project for improving Lynn Harbor, which then was supposed could be efficiently done by leading the backwater of Chelsea Creek and the Saugus River into the improved Lynn (main ship) Channel. The project contemplated the construction of a breakwater of rubble-stone, shown by coarsely broken (parallel)_red lines on tracing, which was to be raised to a height of about 4 feet above the plane of mean high water, and to be started from a point on the western shore of the "Point of Pines," near the junction of Chelsea Creek with the Saugus River, whence it was to extend in a sinuous course for about 9,600 feet in length, to a point on the west side of Lynn Channel, about 1,000 feet below "Sand Point," where it was to end in a round pier, crowned with a light-house. It was proposed to liberally excavate for a channel inside this breakwater, and for a basin north of the turn of the proposed breakwater, which was to serve as anchorage ground for vessels. Nothing whatever has been attempted for carrying out any part of this project, probably on account of its costliness and very doubtful success. 2. Survey of 1883.-All the principal shore points used in connection with the hydrographic part of the survey for locating, by means of transit or sextant, points in the water (soundings, buoys) have been determined by means of triangulations. As the line BE (see tracing) which had served as base for A. Boschke's survey, and was also used by Mr. Sophus Haagensen, assistant engineer, for his survey of the channel in Lynn Harbor made under direction of Col. George Thom, Corps of Engineers, in 1881 and 1882, was found to differ in length on the map of A. Boschke's, from that of Mr. Haagensen's survey, if measured with the scales drawn on these maps, reported to be, respectively, 200 feet to the inch and 1:5000; it was deemed best to carefully determine its length. For this purpose a line located on Lynn Beach, about 4,500 feet long, has been three times carefully measured with a 100-foot long steel tape (due allowance being made for change by temperature), also the angles of the almost equilateral triangle of which line BE formed one of the sides. By computation the length of the line BE was found to be 6,512.13 feet. Assuming line BE on the map of Mr. Haagensen's survey to be of that length, a scale was drawn to correspond, which scale, also adopted for the map of the survey of 1883, somewhat differs from the true scale of 1:5000, measured with which line BE would be about 6,550 feet long. By expansion of paper some slight difference may be accounted for, but in this case it is probably owing to the draughtsman, who made the reduced copy from the map of A. Boschke's survey to the scale of 1: 5000 adopted for the map of S. Haagensen's survey, not having set the pantograph quite correctly with which the reduction was made. The high-water lines in 1883 are almost identically the same as those of 1866; the only changes of any account have taken place on Chelsea Beach, where by deposits of gravel and sand the high-water line has receded for a total length of about 3,300 feet from 0-120 feet, and on the water front of the city of Lynn, where a number of wharves have been extended further out (see full red lines on tracing of A. Boschke's map). As these extensions are mainly pile constructions, and of proportionate small area, no particular account has been taken of them. The low-water lines have been constructed, as near as practicable, from soundings taken in the course of the survey. Soundings. Most of them were taken in accordance with a predetermined plan on lines properly staked and buoyed out by means of transit and sextant. About every eighth sounding on the flats, and in the channels every fourth or fifth sounding, has been located with the sextant, intermediate soundings being timed in. The soundings taken on zigzag lines in the channel were in a similar way, but more closely located. Tide-staffs.-There were used one at the Black Rock Wharf, Nahant, another at the draw-pier of the Boston, Revere and Lynn Railroad Bridge across the Saugus River, and a third at Lampher's Wharf, Lynn. Tide was observed during sounding at the staff nearest to the work. These staffs were established in accordance with marks made previously at the wharves and draw-pier at slack of high water on a calm day, and after being located checked several times at high water. Simultaneous tide observations were taken on one day, the 23d of May, 1883, at the three staffs, but, on account of being delayed in reaching two of the stations in good time, the observers at the Black Rock and Lampher's wharves did not obtain the full series of readings for the entire flood. These observations, recorded on tabular statement No. 6, nevertheless are quite instructive, and prove the importance of referring the soundings to either the one or other tide-staffs, as otherwise it may happen that a depth is recorded differing from the true one half a foot. Current observations.-After the completion of the survey proper it was intended to take current observations, if practicable, simultaneously from a number of stations, in the channels and on flats, on lines crossing the harbor from Chelsea Beach to Lynn and Nahant Beach. As these lines varied from 1 to 2 miles in length, it would have required many boat crews and trained men in charge of them, for carrying out this elaborate project of current observations, be these observations made with surface floats and log lines from small boats moored at the numerous points in channels and on flats previously buoyed out for that purpose or by determining direction and distance traveled by free floats from the buoys with the sextant or transit either from the water or from the shore. The much-prevailing unfavorable weather in June interfered more than anything else with this project. Dense mists and heavy fogs hanging over the shores and waters would frequently obstruct the sight for many hours together, and fresh breezes and boisterous winds or rainy weather would necessitate another suspension of work. On account of these difficulties current observations were mainly confined to the channels, wherein they have been taken as near as practicable simultaneously from two or three places by two and at times three parties with surface floats and log-lines from small boats moored to the keg-buoys marking the places of observations. Besides the current observations made in this manner with surface float and logline attached, a few observations have been made with free floats, for flood and ebb, in the Point of Pines Channel, as well as in the main ship-channel and Black Rock Channel. Whenever it could be done, and the state of the weather and other circumstances were favorable, the current observations have been taken during the influx and reflux of the tide, as frequently from each of the stations marked on the drawing as could be done with the means available. For the surface floats, tin cylinders 2, 4, and 6 feet long, 3 inches in diameter, were used, with log-line attached, direction of floats being determined with the sextant. The free (subcurrent) floats consisted of two cylindrical tin cans 9 inches long, 8 inches in diameter, joined by line so that the lower can was suspended from 6 to 8 feet below the upper one. Changes in the course of floats were noted with the sex tant. The courses taken by the free floats are marked on the drawing of the survey for flood in blue, for ebb in red, lines; time and velocity at start, at intervals of decided change in course, and at end of course are written down, respectively, in blue and red letters and figures, for either flood and ebb. On the drawing of the survey the locations where the current observations with surface floats from fixed stations have been taken are, marked, respectively, A A', B B', C C' C, and D and D'. The several stations occupied in the localities marked by the above letters are represented on the drawing by small circles, from which blue arrowheads are projected for flood in the direction observed for it, and red arrowheads for ebb velocities for flood, at certain hours of tide, are noted down in blue figures and letters; for ebb in red figures. Letters and figures noted down thus, E, I, H, V = 0.18, should be understood to read, "End of first hour velocity eighteenhundredths of a mile per hour"; if an A appears in place of the E, the velocity would be the average for that hour. Observations of wind.-During the period when continuous tide observations were taken, extending from April 30 to June 7 (inclusive), 1883, approximately correct records were also kept by the observers of the direction and force of winds. From these records wind averaged as follows, viz: No. Description of wind. Duration. Hours. Northerly winds, ranging between NNE. and NNW. Northeasterly winds, varying between NE. and NNE., and NE. and ENE. 12345678 5 Southerly winds, varying between S. and SSE., and S. and SSW. 8 Northwesterly winds, varying between WNW. and NW., and NW. and NNW Total 32 135 70 224 25 Southwesterly winds, ranging between SW. and SSW., and SW. and WSW 229 23 198 936 The above statement proves the southeasterly winds to have been the leading winds, followed closely by the southwesterly winds. The greatest velocity of any of these winds did not exceed 20 miles per hour, but the average velocity of the southeast winds was the greatest. Borings.-Those made in 1882, under directions of Colonel George Thom, Corps of Engineers, by S. Haagensen, assistant engineer, have been entered on the map of the survey of 1883. Small red circles show the locality of the boring; the character of the material penetrated, and depth of penetration, are recorded near these circlets. Addition to map of survey of 1883.-To give the whole area over which the tide-water in Lynn Harbor is distributed it required either to extend the survey beyond Lynn Harbor proper over the area of the Saugus River and Chelsea Creek, or to obtain by reconnaissance and from maps of reliable surveys whatever information was required. As a survey of the backwaters would have been expensive and taken too much time, the survey of the lower part of the Saugus River and the largest part of Chelsea Creek, made by A. Boschke in 1866, and forming part of his survey of Lynn Harbor, was adopted after a reconnaissance had proved that no material change had taken place since 1866. From two county and town maps, drawn to different scales, the outlines for the upper parts of the Saugus River and Chelsea Creek, also locations for railroads, turnpike, and the three tidal mills on the Saugus River, shown at E, F, and G on the map of the survey of 1883, were obtained and transferred to this map. These county maps were drawn to comparatively a small scale, and did not quite exactly agree; however, for all practical purposes the information obtained from them is perfectly satisfactory. Plane of reference, bench-marks.--The plane of mean low water has been computed from fifty-seven rises and falls of the tide during the lunation extending from May 6 to June 5, 1883. The average rise and fall of tide above this plane of mean low water is 9.3 feet (see tracing No. 4). The rise of the piers and wharves to which tide-staffs were attached, above the plane of mean low water, has been ascertained and a bench-mark established on the Lynn shore at the month of the Saugus River, on the stone post which marks the end B, of the base line B E. The center of the chiseled top of this stone is in reference 10.28 feet above the plane of mean low water. Result of survey.-The information called for by the Board of Engineers having reference to the breakwater projected in connection with the improvement of this harbor, the lines of the breakwater have been traced on the maps of the surveys of 1866 and |