205 



The sum of the tidal heights in line (7) divided by 24 gives the mean 

 tide elevation, Ho, above the tidal datum, which in this case is Dela- 

 ware River low water datmn. The equation of the primary entrance 

 tide at station 5+000 is then: 



^=i7o+A COS (at—t). 

 =2.48+2.79 cos (a^-118°200. 



395. The equation of the primary tide at station 77 + 000, derived by 

 the same procedure, is: 



2/=2.79 + 1.45 cos {at-73°50'). 



The computed primary tides and the recorded tidal heights at the 

 two stations are plotted in figure 67. They show a satisfactory 

 concordance. 



STA. S+OOO 



STANDARD TIME 



NOV. 2 7 



12 15- \S 21 



I I 



NOV. 28 



I . I . I .1 .1 .1 



"T 1 — T — T — T — n — II — I ' I ' I I I I ' I I I I — r — r — r — r — i 



3 6 9 IS IS" 18 SI £4 



LUNAR HOUR 



PRIMARY TIDE 



RECORDED TIDE o 



Figure 67.— Primary and observed entrance tides, Cliesapeake and Delaware Canal, 



