NORTH PACIFIC 85 



the sea is most often low ; this is, in fact, the general rule for all parts 

 of the ocean at all seasons. Thus, a high swell is reported locally south 

 of Japan, across the mouth of Bering Sea, and off the Alaskan bight 

 as often as one-fifth of the time in August, much as is true of the sea. 

 Similarly, a heavy swell is encountered somewhat more often in the 

 coastal belt off southern California, and off southern Alaska, than it 

 is in the intervening regions, while the irregular area along the Trades, 

 eastward and westward from the Hawaiian islands, outlined in plates 

 IX and XI by the contours for 10 percent "high," is much more exten- 

 sive for swells than for the seas of which they are reminiscent ; a dis- 

 crepancy of this sort has already been discussed for the Atlantic 

 (p. 76). The regions in the western side of the Pacific in mid-lati- 

 tudes, where swells and seas run high more than 10 percent of the time 

 likewise correspond, in general, one with the other, though their pre- 

 cise boundaries differ considerably for any particular frequency that 

 might be selected ; this is due partly, no doubt, because the term "high" 

 has a different meaning in the one case (12 feet and over for swells) 

 than in the other (8 feet and over for seas), but chiefly because waves 

 that have lost the characteristics of a sea so commonly continue to ad- 

 vance for long distances as a swell. 



The swell, also like the sea, runs high considerably more often in 

 summer in the waters between Japan, the China coast and the Philip- 

 pines in the one side of the Pacific than it does along the coasts of Cen- 

 tral America and of Lower California in the other. The consequence 

 is that vessels crossing in summer from Canadian and Californian 

 ports to Japan and to China may expect to find the swell low during 

 more than half of the time until they cross longitude 180°, beyond 

 which the swell is likely to be low somewhat less often, and high 

 somewhat more so (10 percent or more). But the swells, encountered 

 by ships crossing from San Francisco or Los Angeles to the Hawaiian 

 Islands, are likely to be rather heavy for something like one-tenth of 

 the time during the entire voyage, and low considerably less than one- 

 half of the time. 



At the other extreme, the swell is so seldom heavy enough to be of 

 any practical account along the western sector of the equatorial belt 

 of the North Pacific that such of the August reports as mention it at 

 all there class it as "low" more than 80 percent of the time, all along 

 from about the longitude of the Gilbert group westward to the Mo- 

 luccas and to the southern Philippines ; nor do any of the August re- 

 ports mention a high swell at all within this general region. And since 

 the August sea also is reported "low" there, for 63 to 93 percent of the 

 time, and never "high," the region bounded in plate XII by the con- 

 tour for 80 percent low, may be named the most pacific pait of the 

 ocean of that name of any considerable extent north of the Equator. 



