94 TIDES AND BENCH MAEKS 



corresponding difference for low water is called tropic low water diurnal ine- 

 quality, abbreviated to Tropic LWQ. The great tropic range is the difference 

 between higher high and lower low waters, the contraction being Gc. 

 Tropic HWQ = 1.73? — 0.735 = 1.003 ft. 

 " iFF§= 1.404— 1.124 = 0.280" 

 Gc — 1.737 + 1.404 = 3.141 " 

 The mean great diurnal range of tide is abbreviated Gt, and when either 

 tropic inequality is more than a quarter of Mn, we have 



Gt = ^^' + ^'' = 3008h. 



The range of the diurnal wave may be found from the harmonic constants 

 by the formula 



2D, = 2 042 (K, + 0,) (19) 



in which the diurnal wave is represented by 2D,. From (19) we obtain 



2D, = 1.018 ft. for A^assau. 



The perigean and apogean ranges are due to the moon's varying distance, 



and may be obtained from the harmonic constants by the following formulas : 



rn Mn ^^ +IZ.I 2 Ml mi— Ml J 



X[2N+N,-L,-] (20) 



An = Mn - 



.481 m 



M, 



81 si .08 {K, + 0,r 

 2Mlml~ Ml 



X[_2N-{N,-L,)-] (21) 

 in which the words apogean and perigean are abbreviated to their first and 

 last letters. Prom (20) and (21) we find for Nassau 

 Pn = 3.190 ft., and An = 2.124 ft. 



Recapitulation. 



Non-harmonic results tor Nassau, New Providence, Bahamas, from a year of tidal observations 

 beginning July 1, 1903. 



Time Relations. 



Bstablishment of the port, or the mean high water lunltidal interval at full and change " "' 



otthe moon ^ 28.7 



Coi leoted establishment of the port, or the mean of all high water lunltidal Intervals .... 7 22.8 



Mean of all low water lunitldal Intervals 1 ii.8 



tropic higher high water lunltidal interval 7 27.7a 



" lower " 7 14.0 



" higher low " '• " i 34.2 



" lower .. ' ■"■ o 46.0a 



" high water lunltidal interval of the diurnal wave 8 21.9a 



minimum high water lunltidal interval due to phase, or the priming of the tides. ... 7 01.3 



maximum ' " " " " lagging " " .... 7 44.3 



Extreme minimum high water lunltidal interval due to phase and parallax 6 53.6 



" maximum " " " " " " " " 7 52.0 



