94 TIDES AND BENCH MARKS 



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 = 1.737 — 0.735 = 1.002 ft. 

 " LWQ=1A04: — 1. 124^^ = 0. 2S0" 

 (?c = 1.737 + 1.404 = 3.141 " 



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

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



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

 by the formula 



2i), = 2 042 (/r, + 0,) (19) 



in which the diurnal wave is represented by 2Z>i. From (19) we obtain 



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



The perigean and apogean ranges are due to the moons varying distance, 



and may be obtained from the harmonic constants l)y the following formulas : 



,^ .481 Nl , r^, SI si .08 {K, + OOn 



X[_2N-i-N, — L.;] (20) 



.481 Nl , 

 An = Mn— j^-'-j- 



2.1 



.08 {K, + 0,f 



] 



2 3Ilmi~ Ml 



Xl2N-{N,-LS (21) 

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

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

 Pn = 3.190 ft., and An —. 2.124 ft. 



Eecapitulation. 



Non-harmonic results for Nassau, New Providence, Bahamas, from a jear of tidal observations 

 beginning July 1, 1903. 



Time Relations. 



h. m. 

 Establishment of the port, or the mean high water lunitidal interval at full and change 



of the moon 7 28.7 



Corrected establishment of the port, or the mean of all high water lunitidal intervals — 7 22.8 



Mean of all low water lunitidal intervals 1 11.8 



" tropic higher high water lunitidal interval 7 27.7a 



" " lower " '* " " 7 14.0 



" higher low " '• " 1 34.2 



" " lower " " " " O 46.0a 



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



" minimum high water lunitidal interval due to phase, or the priming of the tides — 7 01.3 



" maximum " " " " " " " lagging '* " — 7 44.3 



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



" maximum " " " '* " " " " 7 52.0 



