Chap, n.] theory of Winds. 457 



\vords_, any caufe which produces a fudden rarefadion 

 in any part of the atmoCphere, produces a current of 

 wind towards the part where the rarefaction takes 

 place > winds are, therefore, not only produced by the 

 earth being heated in a particular part, but by thunder 

 ftorms or other electrical phenomena. The rays of 

 the"- fun are alfo fometimes obftruded by clouds or 

 mifts in particular places, and one part of the world, 

 or even of a particular country, will confequently be 

 lefs heated than another ; in that cafe there will always 

 be a current of air from the cold to the warm region. 

 Befides this, the falling of rain, or other circumftances, 

 produce occafional alterations in the temperature ; and 

 whenever thefe take place in any country, they muft 

 be attended with wind. The great Bacon was the firft 

 who attempted a theory of the wind ; and it is to be 

 lamented that his plan has not been purfued by fuc- 

 ceeding philofophers. The following is a (ketch of 

 his general principles, with a few additions by modern . 

 obfervers. 



1 At fea the winds are more regular than at land ; 

 for there nothing oppofes their progrefs, or alters the 

 fun's influence. 



'The air at fea is more equable, as well as more 

 conftant : at land it blows in fits of force and intermif- 

 fion j but at fea the current is ftrong, fteady, and even. 



' In general, at fea, on this fide the equator, the eaft 

 and north winds are moft violent and boifterous : on 

 the contrary, at land, the weft and Couth winds moft 

 frequently produce hurricanes and tempefts. 



' The air is often feen to move in two contrary cur- 

 rents, and this almoft ever previous to thunder. The 

 clouds, in fuch a cafe, are feen to move one way, while 

 ;he weathercock points another. 



'The 



