204 



and 77+000 on November 27-28, 1928 when tide and current measure- 

 ments were made at these stations, at Biddies Point (station 19 + 600) 

 and at Summit Bridge (station 51+200). The day selected is one on 

 which the tides had little diurnal variation. The origin of time is 

 taken at 7 a. m. on November 27, when the record of the observations 

 begins. 



394. Primary entrance tides. — The amplitude, initial phase, and 

 mean elevation of the primary tide at station 5+000, are computed 

 in the following tabulation from the recorded tidal heights at this 

 station, by the method explained in paragraph 360. 



The mean solar time in lines (2) and (5) corresponding to the lunar 

 hours in lines (1) and (4) is derived by successively adding the length 

 of the lunar hour, 1.035, to the initial time at zero hour. The repre- 

 sentative tidal heights, taken in this case from a plot of the recorded 

 tidal heights, on mean solar time, are entered in lines (3) and (6) and 

 summed in line (7). The last six entries are subtracted from the first 

 six in Imes (8) and (9). The values of S2 and C2 and of ^0 and f are 

 then computed from the equations: 



12s2=ho sm 0+hi sin 30° + . . .h-, sin 150°. 

 12c2=/io cos O+/12 cos 30° + . . .hs cos 150°. 



12«2=29.46 

 S2= 2.45 



3. 37 19. 29 

 3.37 



12c2 = -15.92 

 C2= -1.33 



tan f=12s2/12c2=-1.85. 



f=180°-61°40' = 118°20', 

 ylo = S2/sin f=2.79. 

 Ho =2/1/24=2.48. 



