Z792. en philosophical geography. 155 



cf the general trade •windf. 



The general trade wind prevails in all those large 

 oceans that are unincumbered with land for a coij- 

 siderable distance on either side the equator. Hence 

 they reign invariably throughout the whole great South 

 Sea, and the Atlantic Ocean on both sides the equa- 

 tor, and in the Indian Ocean, with little exception to 

 the south of the line. In all those places, in ftiort, 

 which are marked on the map with single darts, the 

 wind always blowing towards that quarter to which 

 the point of the darts are turned throughout the 

 whole year. 



It has been already said that these winds are occa- 

 sioned by the heat of the sun in equatorial regions^ 

 where his rays acting perpendicularly on the earth's 

 surface, are reflected with greater force, and 

 heat the air, upon the whole, to a greater de- 

 gree, and rarifie it more, 'and consequently render it 

 lighter there than on any other part of the globe. In 

 consequence of this expansion, the denser air, in high- 

 er latitudes, flows necefsarily towards the equator, 

 from either side of the globe. This, if not affected 

 by other circumstances, would produce a direct nor- 

 therly wind in the northern, and a southerly wind in the 

 southern hemispheres ; but as the direct influence of 

 the sun is constantly lliifting over the earth's surface, 

 from east to west, in conseqiicnce of the earth's diur- 

 nal motion, an easterly wind, if this Influence alone 

 were to operate, would tlius be produced. P'rom 

 these two causes operating at the same time, the trade 

 winds naturally blow from the N. E. on the north, 

 u 2 



