137 



o 



0) 



-5 



CURRENT 



After first correction 



final correction 



14 



0^ lO 

 U. 



O 5 12 



Lunar Hour after Transit 



Figure 43. — Final adjustment of computed current in Cape Code Canal. 



18 



as in the example chosen, the timing is such that tlie maximum cm-- 

 rents occur at high and low tide. They become smaller as the angular 

 lag, <^, of the primary current increases and the frictional resistance 

 consequently has a less effect upon the currents. 



276. The residuals developed in the example chosen amount to but 

 a few hundredths of a foot. Much larger residuals, and consequently 

 much larger corrections to the velocity, would be produced if during 

 the tidal cycle the surface head varied from a simple harmonic fluctua- 

 tion by as much as a tenth of a foot. As will later be shown, consid- 

 erable distortions of the surface heads in successive sections of a long 

 tidal channel may be produced in the filUng and emptying of the tidal 

 prism at different tidal stages, and other distortions are produced by 

 the diurnal components of the head. If the first computation devel- 



