[ 379 1 



or approaches to the northern tropic, winter reigns in the fouthern' 

 hemisphere, therefore the lower fedlions of the atmofpheric columns 

 are more condenfed by cold, and confequently the upper fec- 

 tions of thofe columns are proportionably rarer (fuppofing the ab- 

 folute weight the fame) than the correfponding fe6lions of the 

 northern hemifphere, where, from the great expanfion ocdifioned 

 by the heat below, a greater part of their mafs reaches to the fame 

 height as the more rarefied part of the fouthern columns. There- 

 fore during our fummer, or the winter of the fouthern hemifphere, 

 the greater part of the intratropical intumefcence flows to the 

 fouth. Halley adds alfo to the fcT/?, in order to preferve the equi- 

 librium; but this feems a miftake, the equilibrium is fupported, 

 by the inceflant circumvolving flow below. The diredlion of the 

 fuperior current is guided only by the. greater or le{r«fr refiflance 

 it meets with ; it muft move, as he himfelf fays, '■'■from thofe 

 " parts where the greatefl heat is'" and confequently towards the 

 colder, which at that height muft be the rarer, and ofter leaft 

 refiftance ; now the weftern parts, over which the fun's influence 

 has not as yet been exerted, are evidently colder than the eaftern, 

 over which the fun has already paflTed, therefore the fuperior 

 current is direded weftward, or in other words a NE. wind pre- 

 vails above. The reverfe takes place in the northern hemifphere 

 during our winter, or in other words a SE. wind prevails in the 



upper regions of our atmofphere. 



Again,. 



