92 FREQUENCY OF WAVE CONDITIONS 



cent), considerably more often than the sea does, suggests that this 

 would prove equally true right across the ocean in this belt, as well as 

 to the southward. And this is certainly the case between New Zealand 

 and Australia, where an average July-August frequency of about 30 

 percent for high swells, but of only about 15 percent for high seas, af- 

 fords still another illustration of the general rule that wherever the sea 

 runs high for any considerable proportion of the time, the swell may 

 be expected to do so even more frequently. In fact the only areas 

 in the South Pacific of any considerable extent, where a high swell 

 has not been reported in frequency as great as 10 percent, for July 

 and August combined, are off the tropical American Coast in the 

 east, along the equatorial belt in the west, and under the close shelter 

 of the more extensive island groups, such as the Fijis and the Ellices. 



The Trades, however, raise a sea higher than 8 feet so much less 

 often in the South Pacific during the northern winter than during 

 the northern summer that the average frequency of the category 

 "high" is less than 1 percent (stated as on the chart), for January 

 and February at 71 out of the 104 squares between the equator and 

 latitude 25° S.. from which a significant number of returns were re- 

 ceived. Indeed, the maximum reported frequency for high seas for 

 this season, along all this belt, is only 11 to 14 percent (off Australia). 

 The prevailing smoothness of the South Pacific is especially striking at 

 this season off South America, when it is necessary to proceed some- 

 thing like 1,000 miles offshore to find high seas in reported frequency 

 as great even as 3 to 11 percent at any individual square, anywhere to 

 the northward of the latitude of northern Chile (lat. 25° S.). Simi- 

 larly, the swell is heavy enough to be reported as "high" only about 

 one-third as often in January and February, as in July and August, 

 throughout the Trade Wind Belt of the South Pacific in general, all 

 of which is in line with common experience. 



And the seasonal contrast is of this same order for seas in the mid- 

 latitudinal belt as well, for even there the January-February chart 

 fails to show a frequency greater than 20 percent for high seas any- 

 where to the northward of the latitude of northern New Zealand on the 

 one side of the South Pacific, or of central Chile on the other. And 

 while a high swell is reported rather more frequently in northern 

 winter from eastern Australia out past New Zealand (0 to 35 percent) 

 than a high sea — as is indeed the usual rule — the seasonal alteration 

 from summer to winter is of the same order for high swells as for 

 high seas throughout such other parts of the South Pacific as the 

 reports cover, as illustrated by the smaller areas enclosed by the con- 

 tours for high swells in 10 percent and in 20 percent frequency in 

 January and February (pi. XV) than in July and August (pi. XI). 



Corresponding, too, to this decrease from July-August to January- 



