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Henry flag-staff," "Lazaretto," "Buchanan," "Fishing Point," "Sollers' Point," "Hawkins' Point," "Fort Carroll Light House," "Sparrows' Point," "Rock Point," "North Point" (upper light), North Point" (lower light), "Bodkin," and "Seven-foot Knoll Light House."

SURVEY OF 1876.-The interest manifested by the municipality of the city of Baltimore in regard to permanent improvements of the harbor took form in May of this year. The Legislature of Maryland, in its session of 1875-76, passed a special appropriation of $5000 for the purpose of a proper topographical survey in furtherance of that purpose. The bill provided for the co-operation of the Coast Survey in the work, and requested the appointment by the President of a Commission composed of the Chief of Engineers, the Superintendent of the Coast Survey, and the U. S. Engineer in charge of harbor and river improvements at Baltimore.

The Commission, appointed as requested, consisted of Major-Gen. A. A. Humphreys, Dr. C. P. Patterson, and Major W. P. Craighill. J. W. Donn, Assistant Coast Survey, was assigned to make all surveys needful for the deliberations of the Commission in the establishment of permanent harbor lines. These surveys were shown upon five sheets of wharf, pier and shore lines, and the same number included full hydrographic details.

For this special survey a careful triangulation was made during July and August, 1876. In the course of this triangulation the following easily recognized points and discoverable with little trouble at the present time were determined: "Bayview Asylum," "Washington Monument," "Light Street Corner," "Gail & Ax's Cupola," "Malt House," "Knabe's Piano Factory," "Chase's Wharf," "Bonded Warehouse," "Abbott's Foundry," "Mill Cupola," "Central Cupola," "Green Cupola," "Elevator B," "Lazaretto," "Iron Foundry,' Parapet," and " Fort McHenry flag-staff." Subsequently the entire wharf-line was measured carefully with a steel tape as a check and for comparison with the plane-table determinations. As usual, the topographical work was done entirely upon the ground, the only record being delineations upon the field sheets. Comparisons

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were frequently made with the measured lines of wharves, piers and docks, and the agreement left nothing to be desired in point of accuracy.

In extending the survey along such parts of the shore as were not occupied by wharves or piers, and which could not be clearly defined. otherwise, a leveling instrument was used to mark out the line of mean high water. This plan was ascertained by the observation of a series of day and night tides extending through two lunar months. Tide stations were established at Henderson's wharf (Fell's Point), Woodall's ship yard (Locust Point), Bollman's wharf (Canton), and at Winans' dock in the Patapsco river. The series was recorded at the Fell's Point gauge, and during intervals free from winds and abnormal tides, simultaneous observations were made to determine. differences of period of maximum of flood and ebb. These differences were found to be less than 15 minutes, or practically inappreciable in the limited tidal flow of the harbor, which the mean of one hundred and fifteen tides show to be 1.16 feet, or .04 feet less than that established for the station at Fort Carroll. The sounding of the harbor was begun early in October and continued without interruption until that part of the area known as Spring Garden was closed by ice. During the progress of hydrographic work the shores of the Patapsco river on both sides were surveyed, scale 1:3600 (300 feet to the inch). The space between the head of the basin and the lines of Canton was mapped on the scale of 1:1800 (150 feet to the inch). The hydrographic survey covered the entire area above the line of the Lazaretto and Marine Hospital wharf, excepting the main branch of the river above the Long Bridge. The area of the basin and harbor to the entrance at Fort McHenry was sounded and plotted on the scale of the topographical sheets that covered the same locality.

On June 1, 1877, the survey was resumed at Spring Garden and in the Patapsco (main branch) between the drawbridge and Brooklyn, west of the bridge.

The recorded details show that in the course of the survey 17,400 soundings were made and 1443 angles measured for determining the position of the boat while sounding in midwater. The positions at

ends of lines were determined by the plane-table. Principal lines of soundings were run parallel to the meridian. Cross or check lines intersected them at right angles. Lines of levels were run between the tide gauges at Henderson's, Bollman's and Woodall's, but no appreciable differences of plane were found. The same result was obtained by simultaneous observation of tide at the several stations mentioned. This, the most thorough and elaborate survey hitherto made in and adjacent to the harbor of Baltimore, is represented by five topographic and five hydrographic sheets.

In March, 1881, Mr. Charles Junken, United States Coast and Geodetic Survey, made a re-survey of that part of the Patapsco lying between Fort Carroll and the line of Marine Hospital Lazaretto.

SURVEY OF 1886.-In June, 1886, at the request of Major N. H. Hutton, Engineer of the Harbor Board, the work of 1876 was supplemented by a verification of the triangulation and its adjustment to more recent computations made by the Computing Division of the Coast and Geodetic Survey Office of the triangulation of the Chesapeake Bay. The purpose of Major Hutton's request, however, was the tracing upon the ground of the Port Warden line established by the Commission of 1876 and its connection with the triangulation in such a way that its identification could be secured by reference to established ground-marks. The Superintendent of the Coast and Geodetic Survey assigned to this work Assistant O. H. Tittmann. Copies of the original plane-table sheets of the special survey of 1876 were in possession of the Harbor Board of Baltimore, and upon these were laid down the Port Warden line of the harbor after due consultation with the engineer of the Board. In conformity with the suggestions of Major Hutton, Mr. Tittmann confined that part of his work to tracing the pier-head lines around the harbor-the bulk-head lines in certain places only being marked.

The method pursued was to transfer the Port Warden line to the original sheets. These sheets were then taken into the field, and in general the points of deflection of these lines were identified by means of the plane-table. They were then referred by distance measurements and deflection angles to stones planted in the streets or side

walks of the city, except where no streets had been opened, as along the middle branch of the Patapsco river, where the stones were set along the high-water line. These stones were connected with the triangulation and their location accurately described in the records.

As a base for the needful triangulation, Assistant Tittmann adopted the same line, Bayview monument, that had been used in 1876, and as the progress of the measurements between the reference stones in the streets disclosed a want of accord between the distances determined by these measurements and those deduced from the triangulation, it was deemed advisable to strengthen and check the triangulation by connecting it with some of the primary stations. Finally, however, on account of the difficulties of recovering the stations proposed and the expense attending their occupation, it was decided to obtain the desired check by the measurement of a base line and its introduction into the triangulation. A site about a mile in length having been selected on Fort Avenue, the measurements were made with the fourmetre contact slide case apparatus and a correction found and applied to the previously accepted distance, Bayview monument. One hundred and seven geographical positions were determined, of which ali but eleven were new.

In the scheme of triangulation carried out by Assistant Tittmann, many points of the work of 1876 were included. Of the one hundred and eleven geographical positions determined, nearly all can be identified and made available for future surveys. The prominent new positions added to the previous lists are: "Grace Methodist Church Spire," "St. James' Church Spire," "Johns Hopkins Hospital," City Hall," "Holy Cross Church Spire," and the "Canton Elevator."

At the end of March, 1887, Major Hutton applied for the assignment of an officer of the survey to execute certain work supplementary to that accomplished by Assistant Tittmann, and Sub-Assistant W. I. Vinal was assigned for that purpose. In connection with the soundings made, some miscellaneous measurements of streets and wharves along the water front were included in his work.