BREAKER CHARACTERISTICS 



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The breakers that develop over evenly sloping beaches are of two 

 chief types, if the wind is not strong enough to interfere with what 

 may be termed their "normal" development. In the one type, the 

 back of the wave continues well rounded up to the instant of breaking 

 (Figs. 22 and 23), whereas its front may become so deeply hollowed 

 that a swimmer, standing on the beach directly in its path and ready 

 to dive through it, may be able to look up for an instant through a 

 sheet of overhanging water, before his head is submerged. The wave 

 forms are very greatly reduced in the act of breaking when the break- 

 ers are of this type, which may be named "plunging." And the event 

 occupies only a few seconds — unless, indeed, the wave is coming in at 



Figure 22. — A breaker of the plunging type, on the coast of New Jersey, showing 

 different stages of development along different parts of the crest. (Woods 

 Hole Oceanographic Institution photograph. ) 



an angle with the shore, in which case it begins to break first at its 

 inshore end, and does so progressively outward along its crest as the 

 latter continues to advance, as is illustrated by the aerial photograph 

 reproduced in figure 24. In breakers of the second type, the backs 

 of the crests, as well as the fronts, become concave as they near the 

 breaking point, so that they more nearly resemble the profile of the 

 steepest possible wave (fig. 25), a shape known technically as "cy- 

 cloid." 



When the tops of their crests final rise to the angle of instability 

 they do not simply fall forward as do the "plunging" type, but they 

 break continuously (but only along their very tops) as they advance, 

 gradually losing in height by the loss of water from their crests as 

 they near the shore. These may be termed the "spilling" type. 



We were fortunate to be in a position to watch the development of 

 both these types of breakers on a recent occasion, while looking out 



