TIDES AND CURRENTS IN BOSTON HARBOR 21 



CURRENT OBSERVATIONS, 1902 



In connection with a general survey preliminary to the construction 

 of the Charles River Dam, the committee in charge obtained current 

 observations at several points in Boston Harbor. These current 

 observations were conducted by W. E. Spear under the direction of 

 J. R. Freeman, chief engineer, and the results were published in 1903 

 by the committee on the Charles River Dam. They were made 

 principally in the channels in four localities, between Boston and East 

 Boston, between Governors Island and Castle Island, between Deer 

 Island and Long Island, and between Long Island and Moon Head. 

 In the first three localities named the observations were taken at five 

 different depths, namely, near the surface, about one-third to bottom^ 

 one-half to bottom, two-thirds to bottom, and near the bottom. In 

 the last location the observations were taken at four depths only. 



The velocities were obtained by current meters, five different 

 meters being used for the different depths. Three of these were 

 Ritchie Haskell meters, one a Fteley & Stearns meter, and the other 

 an Ellis meter. The direction of the current was in general parallel 

 to the axis of the stream. 



The observations were made principally near the mid-channel, 

 where the velocity is greatest, but there were also some observations 

 made at a number of points in the sections across the channels. The 

 results in Table 33 are from the observations in the mid-channel and 

 refer to the several depths indicated. In this table the station num- 

 bers are prefixed by the letter "C" to signify that the observations 

 were made by the committee on the Charles River Dam. 



CURRENT OBSERVATIONS, 1926 



A special tidal current survey of Boston Harbor was begun June 8, 

 1926, by a party under the direction of R. W. Woodworth, of the 

 Coast and Geodetic Survey. The work was continued until August 

 11, 1926, when the party proceeded to Portsmouth, N. H., for a 

 survey of that locality. 



Equipment. — The floating equipment included the two wire-drag 

 launches, Ogden and Rodgers, and the launch Helma, a 55-foot boat 

 which was leased for the period of the survey. In addition to these 

 three launches which were used in the observation of currents, the 

 launch Treasure Trove, a 40-foot boat, was leased as a dispatch boat 

 and was also used for observing currents. Each of the three larger 

 launches had accommodations for a crew of eight men, while the 

 smaller launch had accommodations for six men. All launches were 

 equipped to remain on station for periods of one week at a time. The 

 principal current apparatus ^ in use consisted of current poles, Price 

 current meters, and bifilar current indicators. There was also in use 

 a Pettersson current meter. 



_ Current pole. — The current poles were used in obtaining the direc- 

 tion and velocity of the current near the surface. The pole generally 

 used was 15 feet long and weighted to float uprightly with 1 foot of 

 its length above the water surface. Such a pole would therefore 

 indicate the resultant current for the first 14 feet of depth, which 



J Apparatus used in current surveys is described in considerable detail in Special Publication 124 of 

 the C. & G. Survey. 



