PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
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is the stronger. But if the bottom current be the stronger, and both currents are 
opposite or diverge by a considerable angle (as may rarely be the case in shoal water, 
though perhaps never in deep), the method is made unreliable. 
Fig. 187.— Distribution of density at the surface, February to March, 1920 
In studying the dynamics of any shoal area it is also essential to appreciate 
the effect which the contour of the bottom may have in deflecting the gradient 
currents. This, of course, can not be stated by rule, but usually it is fairly simple of 
interpretation. 
