278 THE PHYSICAL GEOGRAPHY OF THE SEA. 



and 20° north, tlie northeast trade-winds, toward the latter part 

 of January, begin their conflict with the southwest monsoons. 

 The conflict rages in February, and by March the southwest mon- 

 soons in that "field" are considered to have regularly set in. 

 They now remain the dominant wind for upward of six months, 

 and until some time in the early part of September. The north- 

 east monsoons or trades now renew the conflict, which is carried 

 on with more and more vigor until the latter part of November, 

 when they obtain the ascendency, and prevail until the latter part 

 of January, Avhen, as before stated, the southwest monsoons com- 

 mence their annual struggle for the mastery. 



801. In the next field below, i. e., between 15° and 20° north 

 latitude, the northeast monsoons begin to grow light and variable, 

 and to have conflicts with the southwest in February. The pe- 

 riod of this conflict, or change, as it is called, frequently lasts until 

 some time in March, when the force that is calling in and driving 

 the monsoons from the southwest finally gains the ascendant. 

 They then blow steadily until late in September, when the north- 

 east trade-wind forces begin again to assert their ascendency and 

 to renew the conflict on this side through October, by which time 

 the northeast trades or monsoons become the prevailing winds. 

 Thus, by going two or three hundred miles farther from the sup- 

 posed place of heat and rarefaction that give rise to this system of 

 winds, the duration of the northeast monsoons is prolonged nearly 

 a month ; for in this " field" they prevail from November to Janu- 

 ary inclusive, three months, while the southwest last from about 

 the middle of March to the middle of September, say six months. 



802. In the next field below, i. e., between the parallels of 10° 

 and 15°, the southwest monsoons blow about five months, per- 

 haps not quite so long ; they do not commence as early, nor blow 

 so late as in the " field" above. They begin the conflict with the 

 northeast trade-wind forces in the latter part of March, and gain 

 the ascendant in May. They then prevail till October, when the 

 northeast trade-wind forces, escaping from the heated plains of the 

 interior, begin to renew the annual combat which is to get them 

 the victory. They soon achieve it, and maintain the mastery un- 

 disputed till the last of March or first of April. 



