125 



From table IX the corresponding value of is 10°12', and from 

 equation (160): 



5=5.3lVcos 10°12' = 5.27 feet per second. 



From equation (163), the primary current, at the time t after a 

 lunar transit is then: 



y=5.27 sin (m2^+124°020 



250. The head and the primary current are plotted in figure 38. 

 As station 180+30 has been taken as the initial station, and as the 



--\-o,s 



I 



-o 



X. 



--O.^ 



Lunar Hour a^terTransU, 



Figure 38.— Primary current and head in section of Cape Cod Canal. 



stationing is from east to west, westerly currents are positive, and 

 easterly currents are negative. 



251 . As a second example, the value of S in a section of the Delaware- 

 River near the mouth is 0.0000146, the hydraulic radius in the section^ 

 at mid tide, being 19.3 feet. The value of C corresponding to a. 

 coefficient of roughness of 0.025 is 120. Then: 



P=2.18 P/>S= 149,300 



<^=36° 5=2.18Vcos 36° = 1.95 feet per second. 



