Page:Physical Geography of the Sea and its Meteorology.djvu/479

Rh the propriety of excluding all regions which are known to present exceptional cases to the general law. The grouping was not carried beyond lat. 60° north and south, for the lack of observations on the polar side of those parallels. The number of observations thus becoming available was 1,159,353. These were then divided simply into two classes for each belt, viz., polar winds and equatorial winds. They were then reduced to terms of a year, and the average prevalence of each wind in days deduced therefrom, as per Plate XV., and the following table:—

Polar and Equatorial Winds.

852. The null belts.—This plate and table reveal a marked difference in the atmospherical movements north, as compared with the atmospherical movements south of the equator. The equatorial winds of the northern hemisphere are in excess only between the parallels of 10° and 30°; i. e., they are the dominant winds over a zone 20° of lat. in breadth, while the equatorial winds of the southern hemisphere hold the mastery from 35° S. to 10° N.; i. e., they are the dominant winds over a zone 45° of lat. in breadth, while the others cover a space not half so broad. This table, moreover, shows the debatable ground between the winds, or what may be called the null belt in this general movement from poles towards the equator, and from equator towards