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. 

 " ZJF<?=: 1.404 1.124 = 0.280" 

 Gc 1.737 -f 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 



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

 by the formula 



2^=2042(^+0^ (19) 



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



2Z?i = 1.018 ft. for Nassau. 



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 : 



Pn -Mn ^l^+hl 8l * < W iM! 

 Jf t ~2IffmI~ M\ J 



8 -A] (20) 



.481 Nl r 81$ .08 (K, + 00*1 



An = Mn- ~ -^- + [2.1 - ^j^- ^jf~ 



X[2tf (AiL*)] (21) 



in which the words apogean and perigean 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 year of tidal observations 

 beginning July 1, 1903. 



TIME RELATIONS. 



h. in. 

 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 " " " " .............................................. 46. Oa 



" 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. 



