ON CLIMATES AND VtKDS. 70f 



northern and southern currents meet, their joint effect mu«t naturally be to 

 produce a due east wind; but in some parts of the ocean, temporary calms 

 and irregular squalls have been observed to take place of this easterly wind, 

 ■which generally prevails in the neutral parts near the equator. 



The tliird fact, that is, the frequency of westerly winds between the ^-^'^ESg ^ 

 latitudes 30' and 40°, has not yet been sufficiently explained. The most 

 probable cause of this circumstance is, that the current of heated air, which ^*^/:/>r, 

 we have liitherto neglected, and which passes, in the upper parts of the 

 atmosphere, from the equator each way towards the poles, and whiJi, being 

 the converse of the trade wind, must be a south west and north west \viud> 

 in the different hemispheres, becomes here sufficiently cool to descend and mix 

 with tke lower parts of the atmosphere, or to carry them along by itslateral fric- 

 tion; and while it descends to complete the circle, necessary for supplying the 

 current to tlie equator, its motion with respect to tlie horizon nuist btcomeat a 

 certain time due M-est, since the cause which stops its progress n.rthwdnis, has 

 no tendency to impede its motion eastwards. The outN\ard bound East India 

 ships generally make their easting in about 36" south latitude. It is probably 

 also on account of the rotatory motion of the earth, that southwest winds are 

 more common in our latitudes than south east, and north east than northwest. 



Among the local modifications to be considered in the fourth place, we 

 may reckon the greater indistinctness of the third effect in the northern than 

 in the southern hemisphere, a circumstance which is explained from the more 

 irregular distribution of sea and land: for between 30° and 40° south 

 latitude the ocean is scarcely any where interrupted. In lower latitudes also, 

 near the west coast of Africa, the winds are so much deflected towards the 

 land, as to become in general westerly instead of easterly. 



The monsoons, which constitute the fifth remarkable circumstancey are 

 so called from a Malay word, denoting season. They are occasioned by the 

 peculiar situation of the continent of Asia, on the north side of the equator. 

 From April to September, the sun having north declination, the heat on this 

 continent, a little north of the tropic, is very intense, and the general 

 current is consequently towards the north. The air, therefore, coming 

 from douth latitudes towards the equator, becomes, on account of tlje defi- 



