18 U. S. COAST AND GEODETIC SURVEY 



TIDE OBSERVATIONS, MISCELLANEOUS SERIES 



Besides the principal series of tide observations at the navy yard 

 and at Commonwealth Pier No. 5, there have been a number of 

 shorter series in various parts of the harbor which were obtained 

 from time to time in connection with other hydrographic work. The 

 observations have been reduced and compared Avith simultaneous 

 observations at certain standard ports, and the results are given in 

 Table 29. For the comparisons the observations at the navy yard 

 and Commonw^ealth Pier No. 5 were used as far as practicable, but 

 whe?i observations at either of these stations were not available 

 other ports of reference were used. 



The results obtained from very short series of observations may be 

 affected by accidental conditions prevailing at the time of the obser- 

 vations, which would be largely eliminated in a longer series. For 

 this reason such results are to be considered only as approximate 

 values and subject to adjustments based upon other tidal data for 

 the same general locality. 



Adjusted tidal data. — Table 30 contains adjusted tidal results for 

 the tide stations which are enumerated in the preceding table. In 

 obtaining these adjusted values consideration was given to various 

 factors involved. The results from the more recent observations 

 were given preference to those of earlier observations, not only because 

 of possible changes in the tide due to changes in the configuration 

 of the harbor but also because the later series were presumably made 

 under more favorable conditions. The difficulties of maintaining 

 accurate time in the earlier years were undoubtedly much greater 

 than during more recent years. 



In maldng the adjustment consideration was given to the harbor 

 as a whole. The times of the high and low waters throughout the 

 harbor differ by only a small amount, the tides at the navy yard 

 occurring about a quarter of an hour later than at Boston Light. 

 The mean range of tide at the navy yard is about 0.7 foot greater 

 than at Boston Light. The mean range throughout the harbor varies 

 from 9 to 10 feet. 



The spring and neap ranges are included in this table. For the 

 two primary stations at the navy yard and Commonwealth Pier No. 

 5 these ranges were obtained directly from the observations. For 

 the other stations they were derived by applying to the mean range 

 factors based upon the observations at the primary stations. 



Information in regard to the distance that tidal influences extend 

 up the several rivers is included in Table 30 for convenience of 

 reference. 



CURRENT OBSERVATIONS, 1847 AND 1848 



In connection with a hydrographic survey of Boston Harbor under 

 the direction of Lieut. Commander Charles H. Davis, current obser- 

 vations were taken between June 9 and October 22, in 1847, and 

 between June 7 and October 21, in 1848. A sailing schooner, the 

 U. S. S. Gallatin, was used in maldng the observations, and the work 

 was under the immediate supervision of Lieut. John N. Maffitt. 

 Although the apparatus used is not described in the records, it is 

 presumed that the velocities were obtained by a log line and that 



