[ 63 ] 



mean heat of the whole fpace between lat. o and lat. 30*^ Is 

 only feven degrees bfs than the mean heat under the asquator, 

 the difference of denfity is not fo great as to caufe any rapid 

 collaplion of the fuperior columns within that fpace ; but from 

 lat. 30 to lat. 60° (a much fmaller fpace) the mean annual heat ; 

 over the ocean differs from that of lat. 30° by nearly fourteen 

 degrees * ; therefore the rapidity of the upper current towards 

 the polar regions is much greater^ and frequent interruptions mufl 

 take place, during which the weight of the atmofphere will be 

 diminifhed. And hence, notwithftandiixg the high winds that 

 frequently prevail between the tropics, the barometer varies 

 inconfiderably and but feldom, whereas without them^ the varia? 

 tions are frequent and confiderable, nearly in proportion to the 

 diftance from the asquator ;. and thus the fecond obfervation is 

 fufEciently explained. 



As the tides of the fuperior atmofphere flow in greater quan- 

 tity where they meet with leaft refiftance, the diredion. of this 

 maximum of quantity is different, in different feafons of the. year, 

 and on different places. 



During the fummer of the northern hemifphere, as winter 

 then prevails in the fouthern, the denfity of the asquatorial air 

 becomes fuperior to that of the fouthern air at a much lower 

 height than that at which it becomes fuperior to the northern, 

 which is itfelf expanded by the prefence of the fun in the 

 northern tropic j therefore the fuperior exuberance is chiefly 



* Eftimate of the Temperature of different Latitudes, p. 17.- 



poured 



