SOUTH ATLANTIC 81 



season, for the frequency with which waves of 20 feet and higher have 

 been reported for the year as a whole is very nearly the same for the 

 South Atlantic, in the latitude of southern Argentina (12 percent), 

 as in the North Atlantic between Newfoundland and England (13 

 percent. See table 8, p. 21.) 



On the other hand, the seasonal expansion and contraction of the 

 limits of the area where a high sea is commonly encountered in the 

 Southern Hemisphere is the reverse of that in the Northern, as illus- 

 trated by the fact that while, in the latter, it is in January and February 

 that the contour line for high seas in 10 percent frequency approaches 

 nearest to the equator, it is in August that this happens in the South 

 Atlantic. This difference was of course to be expected from the fact 

 that the northern winter is the stormy season in the Northern Hemis- 

 phere, whereas it is stormiest in the Southern Hemisphere during the 

 northern summer. Correspondingly, it is during the northern winter, 

 when the high and mid-latitudes of the North Atlantic are the most 

 often troubled with high seas, that the sea is the least often rough in 

 the corresponding belt of the South Atlantic. 



A heavy swell, too, is reported considerably more often throughout 

 all but the subequatorial region of the South Atlantic during the 

 northern summer than it is in the North Atlantic, for tliis same reason, 

 the opposite being true in northern winter. This again is consistent 

 with the differences in seasons in the two hemispheres. During the 

 stormy half of the year, too (northern summer in this case), a heavy 

 swell has been reported generally throughout low and mid-latitudes 

 of the South Atlantic considerably more often than a high sea has, 

 much as is true of the North Atlantic in the northern winter, and no 

 doubt for similar reasons (p. 78). 



Although the number of reports received from the South Atlantic is 

 small except along the two coasts, they are enough to show that the 

 frequency distribution of seas of different heights there in the northern 

 summer is roughly a mirror picture of the sea pattern of the North 

 Atlantic ; i. e., while a heavy sea is the most common in high latitudes 

 and least so in low, in both oceans, the area where the sea is low for 

 more than half the time extends farthest from the equator in the 

 eastern side in the Southern Hemisphere, but in the western side in 

 the Northern. In northern winter, high seas, and high swells as well, 

 are considerably more common off the coast of Africa at corresponding 

 latitudes, to the southward of about 20° S., than off the coast of South 

 America, which is true of high swells in the northern summer as well. 

 (See tables 21 and 22.) 



