MONSOONS. 365 



or of any other great river, to his senses. The greatest move 



THAT CAN NOW BE MADE FOR THE ADVANCEMENT OF METEOROLOGY IS TO 

 EXTEND THIS SYSTEM OF CO-OPERATION AND RESEARCH FROM THE SEA TO 

 THE LAND, AND TO BRING THE MAGNETIC TELEGRAPH REGULARLY 

 INTO THE SERVICE OF METEOROLOGY. 



CHAPTER XVI. ' 



§ 681-711. — MONSOONS. 



081 . The cause of. — Monsoons are, for the most part, trade-winds 

 deflected. When, at stated seasons of the 3^ear, a trade-wind is 

 turned out of its regular course, as from one quadrant to another, 

 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 ; these winds, 

 carrj'ing their fuel (§ 254) with them in vapour, have their equi- 

 librium still further disturbed by the heat which is liberated 

 when that vapour is condensed. Thus, with regard to the N.W. 

 and the S.W. monsoons of the Indian Ocean, for example : a force 

 is exerted upon the N.E. trade-winds of that sea by the dis- 

 turbance 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 N.E. monsoons would blow the year round ; there 

 would be no S.W. monsoons there ; and the N.E. winds, being 

 perpetual, would become all the year what in reality for several 

 months they are, viz., N.E. trade-winds. 



682. The region of. — Upon India and its seas the monsoon 

 phenomena are developed on the grandest scale. These remark- 

 able winds 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 K.E. trades, are here called N.E. monsoons, because, 



