Tattle — Changes in Elevation of Land and Sea. 337 



was given as 14*6 ft. above M. L. W. "from the observations of 

 1853 verified in 1873"; and that the observations of H. T. L. at 

 Boston from . 1853-5 and 1870-3 have substantially the same 

 relative elevations and yearly fluctuations. 



From October 2d to 30th, 1886, a series of comparative tidal 

 observations were carried out at Governor's Island and Sandy 

 Hook, and the resulting M. S. L. corrected for annual inequality 

 above zero of staff at Governor's Island was 4*200 ft., with zero 

 of staff at that time 16'43 ft. below B. M.„ making M. S. L. 1*973 

 ft. above Battery datum. 



We next have the tidal observations at Sandy Hook, which 

 are as follows : 



M. S. L. and H. T L 

 above Sandy Hook 

 datum. 

 6*74 ^ 

 6*90 

 7*06 

 6*87 

 6*84 

 6*89 J 



6*90 ) H. T. L. from high 



7*02 J and low waters 

 (7*17) )- (values in parenthe- 

 (6*82) | sis partly estimated) 

 (6-90) ) 



1 



Year. 

 1876 

 1877 

 .1878 

 1879 

 1880 

 1881 



1882 

 1883 

 1884 

 1885 

 1886 



1887 

 1888 

 1889 

 1890 

 1891 

 1892 



Equivalent H. T. L. at 



Governor's Island 

 above Battery datum. 



! M. S. L. from hourly 

 ( heights 



6*91 

 7*00 

 7*13 



7*05 

 7*09 

 7'05 



M. S. L from hourly 

 heights 



•774 

 •934 

 •094 

 •904 

 •874 

 •924 



•934 

 •054 

 204 

 •854 

 •934 



•944 

 •034 

 •164 



•084 

 •124 



•084 



The observations made at Sandy Hook were referred to a 

 plane 17*63 below B. M. T.,"** and are reduced to Battery datum 

 by means of the simultaneous observations for the four years 

 1876-1879 at Governor's Island and Sandy Hook. 



While spirit levels have been taken between Sandy Hook and 

 Governor's Island, yet, owing to the considerable distance of 

 the run, they are probably in error more than levels derived 

 from the simultaneous tidal observations. 



The levels derived from the four years of tidal observa- 

 tions agree almost precisely with the levels obtained from the 

 simultaneous tidal observations in October, 1886, and are more 

 suitable to reduce the Sandy Hook observations to simultaneous 

 ones at Governor's Island than the spirit levels. From the 

 spirit levels of 1887 as revised in 1899, the elevation of B. M. 



* Described in C. and G. S. Report for 1887, appendix 14. 



" 1899, page 472. 



