TIDES AND CURRENTS IN BOSTON HARBOR 49 



CROW POINT, HINGHAM HARBOR ENTRANCE 



The foUowing bench marks are referred to the Boston standard 

 "datums through the primary tide station at Commonwealth Pier 

 No. 5, by a comparison of simultaneous tides consisting of 37 high 

 waters and 36 low waters observed during the period June 19 to 

 July 8, 1926: 



Bench mark 1 (established in 1926) is a Coast and Geodetic Survey standard 

 disk, stamped "1/1926," cemented in a drill hole on top of stone sea wall north- 

 west from dock and about halfway between dock entrance and shore. Elevation, 

 9.44 feet above sea-level datum; 14.31 feet above Boston low- water datum. 



Bench mark 2 (estabhshed in 1926) is a Coast and Geodetic Survey standard 

 disk, stamped "2/1926," cemented in a drill hole on top of stone sea wall on 

 main shore line about 20 feet south of dock entrance at a turn in the wall. Eleva- 

 tion, 9.00 feet above sea level datum; 13. S7 feet above Boston low-water datum. 



Bench mark 3 (established in 1926; is a Coast and Geodetic Survey standard 

 disk, stamped "3/1926, " cemented in a drill hole on top of stone sea wall on main 

 shore Une about 100 yards northwest of dock entrance at a sudden bend in the 

 shore Une. Elevation, 9.33 feet above sea-level datum; 14.20 feet above Boston 

 low-water datum. 



TABLES 



The following tables give the results which have been obtained 

 from the observational data discussed in the preceding pages. Ex- 

 planations of the terms used will be found in the text. A list of the 

 tables follows: 



Page 



1. Mean lunitidal intervals and duration of rise of tide, Boston Xavv 



Yard 50 



2. Mean high and low water on original tide scale, Boston Navy Yard.. 50 



3. Mean high and low water referred to sea-level datum, Boston ^^avv 



Yard 51 



4. Mean range of tide, Boston Navy Yard 51 



5. Monthlv extreme high water above sea-level datum, Boston Xavv 



Yard 52 



6. Monthly extreme low water below sea-level datvmi, Boston Navy 



Yard 54 



7. Mean tide level on original tide scale, Boston Xavy Y'ard 56 



S. Mean tide level referred to sea-level datum, Boston Xavy Y'ard 56 



9. High-water lunitidal interval, Commonwealth Pier Xo. 5 56 



10. Low-water lunitidal interval. Commonwealth Pier Xo. 5 57 



11. Duration of rise of tide, Commonwealth Pier Xo. 5 57 



12. Mean high water on tide staff, Commonwealth Pier Xo. 5 57 



13. Mean high water above sea-level datum. Commonwealth Pier Xo. 5-. 58 



14. Mean low water on tide staff. Commonwealth Pier Xo. 5 o8 



15. Mean low water below sea-level datum, Commonwealth Pier Xo. 5-. 58 



16. Mean range of tide, Commonwealth Pier Xo. 5 59 



17. Mean range corrected for longitude of moon's node. Commonwealth 



Pier Xo. 5 59 



IS. Monthlv extreme high water above sea-level datum. Commonwealth 



PierXo. 5 60 



19. Monthlv extreme low water below sea-level datum. Commonwealth 



Pier"Xo. 5 60 



20. Mean tide level on tide staff. Commonwealth Pier Xo. 5. 61 



21. Mean tide level referred to sea-level datum. Commonwealth Pier 



Xo. 5 61 



22. Mean sea level on tide staff. Commonwealth Pier X'o. 5 61 



23. Mean sea level referred to sea-level datum, Commonwealth Pier 



Xo. 5 62 



24. Difference between mean sea level and mean tide level, Commonwealth 



Pier Xo. 5 62 



25. Summarv of time relations, Boston Xavv Y'ard and Commonwealth 



PierXo. 5 1 62 



26. Summary of ranges and inequalities, Boston Xavy Yard and Common- 



wealth Pier Xo. 5 63 



