TIDES AND CURRENTS IN BOSTON HARBOR 45 



This bench mark has also been designated as " Navy Yard B. M. 1," but it should 

 be distinguished from the original bench mark 1 described above. Elevation, 

 9.455 feet above sea-level datum; 14.33 feet above Boston low-water datum. 



Bench mark 3 (established in 1916 by N. H. Heck) is a standard Coast and 

 Geodetic Survey brass disk set horizontally in the granite block at the head of 

 United States Navy Dry Dock No. 2 at Charlestown. Elevation 8.957 feet 

 above sea-level datum; 13.83 feet above Boston low-water datum. 



Navy-yard bench mark 8 is at the head of Dry Dock No. 2 in the Charlestown 

 Navy Yard in the top of the masonry about 1 foot north of bench mark No. 3. 

 A chiseled square. Elevation, 9.485 feet above sea-level datum; 14.35 feet above 

 Boston low-water datum. 



Navy-yard bench mark 10 is north of the tennis courts in the Chailestown Navy 

 Yard, in the pier supporting a column on the southeast side of an octagonal 

 building. A chiseled square. Elevation, 13.307 feet above sea-level datum; 

 18.18 feet above Boston low-water datum. 



Navy-yard bench mark IS is in the Charlestown Navy Yard, at the corner of 

 Second Avenue and Thirteenth Street, in the top of the lower course of masonry 

 at the southwest corner of building 75. A chiseled square. Elevation, 10.945 

 feet above sea-level datum; 15.81 feet above Boston low-water datum. 



Navy-yard bench mark 19 is in the Charlestown Navy Yard, at the corner of 

 Fifth Avenue and Sixteenth Street, in the top of the lower course of stone at the 

 northeast corner of building 77. A chiseled square. Elevation, 12.979 feet 

 above sea-level datum; 17.85 feet above Boston low-water datum. 



Bench mark " Waverly House" is a Boston city bench mark on the right outer 

 corner, facing the building, of the second stone step at the entrance to Waverly 

 House on the City Square. A point on the step. Elevation, 18.140 feet above 

 sea-level datum; 23.01 feet above Boston low-water datum. 



Bench mark F2, near Charlestown, is vertically in the center of the west side 

 of the fourth pier from the eastern or Charlestown end of the "Prison Point 

 Bridge," which is a viaduct carrying Prison Point Street over the railroad tracks 

 and connecting East Cambridge and Charlestown. A brass disk. Elevation, 

 11.575 feet above sea-level datum; 16.44 feet above Boston low-water datum. 



BOSTON (CENTRAL PORTION) 



The following bench marks are referred directly to the Boston 

 standard datums by spirit-leveling connections: 



Bench mark "Post Office" is a Weather Bureau benchmark on the post-office 

 building at the corner of Milk Street and Post Office Square, in the corner stone 

 at the southeast corner, 1 foot above the sidewalk. Bench mark is a chiseled 

 square. Elevation, 14.587 feet above sea-level datum; 19.46 feet above Boston 

 low-water datum. 



Bench mark "83 South Street" (established by Boston city engineers) is a 

 Boston city bench mark on the lower iron step at 83 South Street. The left 

 outer corner of the step, facing the building. Elevation, 12.785 feet above sea- 

 level datum; 17.66 feet above Boston low-water datum. 



Bench mark J2 (established in 1923 by E. B. Roberts) is a Coast and Geodetic 

 Survey standard disk 306 feet south of the south end of the train shed at the 

 Southern Union Station, 213 feet south of signal bridge No. 1; 63 feet north of 

 signal bridge No. 5; 4}/^ feet east of an easterly approach track; in the top of 

 the stone coping at the south end of the iron railing. Elevation, 19.308 feet 

 above sea-level datum; 24.18 feet above Boston low-water datum. 



Bench mark "B. & A. mileage 0.40" is on the northwest corner of the end 

 capstone of the retaining wall at mileage 0.40 on the Boston & Albany Railroad 

 and also on the New York, New Haven & Hartford Railroad, south of the tracks 

 of the latter railroad. A chiseled square. Elevation, 12.123 feet above sea- 

 level datum; 16.99 feet above Boston low-water datum. 



Bench mark "B. & A. mileage 0.61" is on the northeast corner of the central 

 pier of the Boston & Albany Railroad bridge No. 3 at mileage 0.61. A chiseled 

 square. Elevation, 1.542 feet above sea-level datum; 6.41 feet above Boston 

 low- water datum. 



Bench mark H2 (B. & A. mileage 1.19) is set horizontally in the footing at 

 the south end of the east center pier of the Boston & Albany Railroad bridge at 

 mileage 1.19, which is the second overhead bridge south of the Trinity Place 

 depot of the Boston & Albany Railroad. A brass disk. Elevation, 1.371 feet 

 above sea-level datum; 6.24 feet above Boston low-water datum. 



81772—28 4 



