HEIGHT 19 



Another reason why the waves that accompany strong gales usually 

 are not as high as theory demands is that the increase in the height of 

 a wave is not likely to be continuous throughout the period of its 

 development, as it is represented in tables 4 and 5. This is partly 

 because the wind is gusty and does not blow steadily at maximum 

 strength. But it is also due to the fact that the tops of the crests of 

 waves that are being acted upon by strong winds frequently break, 

 whereupon they lose more or less in height. They then gradually 

 build up once more (as anyone favorably situated can easily see), to 

 break again, and so on. Or they may break continuously along the 

 tops of their crests for considerable periods, which hinders their gain- 

 ing in height as rapidly as they would otherwise do under a wind of a 

 given strength. This process is discussed more fully on page 31, in 

 connection with the steepness of waves. 



A fourth phenomenon directly tending to reduce the heights of the 

 waves in stormy weather, and one with which seamen are familiar, 

 is that the waves often are not at their highest when the wind is blow- 

 ing the most fiercely, but after it has begun to die down, probably 

 because the most violent gusts carry the tops of the crests off bodily, 

 thus reducing the heights of the waves for the time being. 



The relationship between storm waves and the winds that they ac- 

 company is complicated further by the fact that the stronger gales of 

 stormy latitudes "commonly come in groups, one succeeding another 

 after a short interval of time. Thus there may be a stormy month 

 during which one cyclonic storm quickly succeeds another, all pursuing 

 the same general track across the ocean. Between times the sea never 

 settles down but heaves with a heavy swell * * * No sooner does 

 a cyclone brew upon the North Atlantic in such a season than the wind 

 in the righthand, rear quadrant of the depression travelling towards 

 Europe immediately steepens this swell into great storm-waves, as 

 happened in the Bay of Biscay on December 21st, 1911 * * *" 

 (Cornish, 1934, p. 29). 



Discussion in the literature of the relationship between wind and 

 waves leads to the very important conclusion (borne out by a great 

 number of observations at sea) that waves do not continue to gain in 

 height indefinitely under a given wind, but that there is a limit to their 

 final heights, no matter how long the wind may have been blowing. 

 Moreover the waves grow much more rapidly at first than later, and 

 when a wave has attained about 75 to 80 percent of the maximum 

 height, for a given wind (see table 7), its further growth is very 

 slow. 



We should caution the reader here that the word "fetch," as applied 

 to the development of ocean waves, does not mean simply "sea room," 

 as one might gather from a cursory reading of writings on the subject, 



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