364 THE PHYSICAL GEOGRAPHY OF THE SEA. 



CHAPTER XYI. 



§ 681-711. — MONSOONS. 



681. Monsoons are, for the most part, trade- winds deflected. 

 The cause of. When, at stated seasons of the year, a trade-wind 



is turned out of its regular course, as from one quadrant to an- 

 other, it is regarded as a monsoon. The African monsoons of 

 the Atlantic (Plate VIII.), the monsoons of the Gulf of Mexico, 

 and the Central American monsoons of the Pacific are, for the 

 most part, formed of the trade-winds which are turned back or 

 deflected to restore the equilibrium which the overheated plains 

 of Africa, Utah, Texas, and New Mexico have disturbed. Thus 

 with regard to the northeast and the southwest monsoons of the 

 Indian Ocean, for example: a force is exerted upon the north- 

 east trade-winds of that sea by the disturbance which the heat 

 of summer creates in the atmosphere over the interior plains of 

 Asia, which is more than sufficient to neutralize the forces which 

 cause those winds to blow as trade- winds; it arrests them and 

 turns them back ; but, were it not for the peculiar conditions of 

 the land about that ocean, what are now called the northeast mon- 

 soons would blow the year round ; there would be no southwest 

 monsoons there ; and the northeast winds, being perpetual, would 

 become all the year what in reality for several months they are, 

 viz., northeast trade-winds. 



682. Upon India and its seas the monsoon phenomena are de- 

 The region of. vclopcd on the grandest scale. They blow over all 



that expanse of northern water that lies between Africa and the 

 Philippine Islands. Throughout this vast expanse, the winds that 

 are known in other parts of the world as the N.E. trades, are here 

 called N.E. monsoons, because, instead of blowing from that quar- 

 ter for twelve months, as in other seas, they blow only for six. 

 During the remaining six months they are turned back, as it were; 

 for, instead of blowing toward the equator, they blow away from it, 

 and instead of N.E. trades we have S.W. monsoons. 



