1887.] 



Constants for Table Bay and Algoa Bay. 



255 



Table I. 



Table Bay. 



' Age ' of tide 



= 26-4 



,Mean height above ft 



datum-line = 2 • 37 



S, 



ft 



ft 



H„,= l-60 (H'=019 



K^= 67° (K' = 124° 



Hs =0-68 fHo=006 







Ks = 93° 



K. = 250° 



ft 

 H" =0-18 



K" = 93° 



H. 



ft 

 0-06 



Kp= 124° 



h m 



*Mean' establishment = 2 19 



S, 



Algoa Bay. 



= 32-0 



ft 

 = 2-34 



H^ = l-76 



H' = 016 



K..= 97° K' = 146° 



H. 



ft 

 :0-83 







K« =128° 



H" =0-23 



K" = 128° 



ft 

 H. = 0-05 



Ko = 280^ 



Hp = 0-05 

 Kp = 146° 



h m 



= 3 21 



The diurnal tides are therefore small at both places, but they are quite 

 sensible. 



The * mean ' establishment hitherto used for Table Bay is 2^ 43"*, 

 so that the considerable correction of 24"* must be applied to the 

 average of the predicted times of high water. This correction to the 



old value may be due partly to the different position of the gauge in 

 the Bay, but more probably to an error in the statement that the times 



V of high water at the Naval Yard, Simon's Bay, and at the South 

 Jetty, Cape Town, are coincident : for unless special precautions are 

 taken in the erection of a tide-gauge to annul the effects of wave- 

 disturbance it is no easy matter to determine the time of high water 

 from the diagram to a good many minutes. 



The * vulgar ' establishment, or time of high water at full and 

 change of the Moon, is 2^ 33"*. The * vulgar ' establishment given for 

 Algoa Bay on the charts is 4^, but Capt. Skead, R.N., has pointed out 

 that the observations on which this result depends were taken at a 

 station some ^ay up the river and that the value for the Bay should 



hQ considerably less : my results make it 3^ 39"*. 



