WINDS. 



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of it from the south, to fill up and restore the equilibrium, produces 

 the southerly Monsoon, which blows with great regularity. 



The Monsoons of the West Coast of Africa prevail from the latitude 

 of Madeira to the Cape de Verdes ; thence south, extending into the 

 Bight of Benin, and as far as the Cape of Good Hope, and are the 

 next to claim attention. 



They are divided into the northwesterly, westerly, southwesterly, 

 and northeasterly Monsoons. The first three blow towards the land, 

 whilst the last, called by the natives the "harmattan," blows from the 

 land to the sea. 



The duration of these Monsoons is very unequal ; the former lasting 

 some nine months, from March to December, while the latter rarely 

 endures three months. Like the Monsoons of the coast of Brazil, the 

 direction of these winds depends somewhat on the trend of the coast 

 and the position of the sun in declination, by which the continent of 

 Africa is heated and the rarefied areas maintained. The current 

 of air rushes towards the heated areas which are nearest ; and con- 

 sequently, on different parts of the coast, the wind changes its direction, 

 so that it is found to flow from the south to the northwest by the west. 



The flow from the west under the equator extends nearly across 

 the Atlantic Ocean, between the two continents, in a cuneiform shape, 

 from the month of June to September; after which time it ceases, 

 calms, and then the " harmattan" prevails from December till March, 

 with occasional intermissions. 



The character of these Monsoons is different ; — that from the south- 

 ward and westward is always attended with rain, while the northeast 

 is a cold and very dry wind, flowing from the highlands of Africa. 

 It seeks the heated areas of the ocean, but does not extend more than 

 a hundred and fifty to two hundred miles from the coast. 



There are other periodical winds, which have an extensive range, 

 but of which our knowledge is as yet very limited. I have reference 

 to the winds which sweep across the great deserts of Africa, Asia, and 

 America. In order to trace these, we require many more observa- 

 tions than we have ; but enough is known to establish the fact that 

 the easterly and northerly winds in Africa and Asia prevail during 

 nine months of the year, and are succeeded by those from an opposite 

 direction. In the Mediterranean these winds which flow towards 

 Africa have been long known by the name of the iEtesian winds. 



A denser and colder aerial current also flows from the Caucasus, in 



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