THE BAHAMA ISLANDS 95 



Height Relations. 



Ft. 



Mean of all high waters on fixed tide staff 4.332 



" low " " " 1.698 



" higher high waters on fixed tide staff 4.640 



" " lower low " " " 1.632 



" of the tropic higher high waters on fixed tide staff 4.728 



" " " lower " " " " 3.726 



" " " higher low " " " 1.867 



' " " lower " " " " 1.687 



" Spring high water on fixed tide staff 4.540 



low " " " 1.489 



" Neap high " " " 4.079 



" low " " " 1.950 



" Perigean high " " " ... . 4.610 



" " low " " •' 1.420 



" Apogean high " " " 4.077 



low" " " 1.953 



" sea level from hourly heights of the sea, on fixed tide staff' 2.991 



" half-tide level from high and low waters, " " 3.015 



Ranges, Inequalities, etc. 



Ft. 



Mean range of all tides 2.634 



" " Springtides 3.051 



" Neap " 2.129 



" " the great tropic tides 3.141 



"small " " 1.859 



" " tides from mean higher high to mean lower low waters — 3.008 



" " Perigean tides 3.190 



" " Apogean " 2.124 



" " the tropic diurnal wave 1.018 



" tropic high water diurnal inequality 1 .002 



low " " " 0.280 



" age of the phase tides Id Oh 



" " " parallax tides Id 18h 



diurnal " — Od 3h 



ANNUAL VARIATION IN MEAN SEA LEVEL AT NASSAU. 



Date. Sea level Date. Sea level Date. Sea level Date Sea level 



feet. feet. feet. feet. 



Jan. 1 -.3 Apr. 1 -.1 July 1 +.1 Oct. 1 +.3 



" 16 -.4 " 16 -.1 '■ 16 +.2 " 16 +.2 



Feb. 1 -.4 May 1 Aug. 1 +.2 Nov. 1 +.1 



" 16 -.3 " 16 O " 16 +.3 " 16 



Mar. 1 -.3 June 1 +.1 Sept. 1 +.3 Dec. 1 -.1 



" 16 -.2 " 16 +.1 " 16 +.4 " 16 -.2 



The above table was computed from the formula 



X = Sa COS (h — Sa") + Ssa cos (27t — Ssa°) 

 where x = height of mean sea level, + when above, — ■ when below the mean 

 of entire year. 



h = the mean longitude of the sun. 



The other symbols are the harmonic constants for the annual and semian- 

 nual inequalities. The values in the table do not exactly average zero, on ac- 

 count of fractions neglected in reducing to a single decimal place. 



