Magnetism and the Trade Winds. 277 



I considered the manifold beauties in the whole -system of 

 terrestrial adaptation : — 1 reflected what a perfect and won- 

 derful machine is this atmosphere : — how exquisitely balanced 

 and beautifully compensated it is in all its parts, — we all know 

 that it is perfect: — that in the performance of its manifold 

 offices it is never once left to the guidance of chance, no, not 

 for a moment : — therefore I was led to ask myself, why the 

 air of the NE. trades when arrived at the zone of equatorial 

 calms, should, after ascending, rather return to the north 

 than the south. Where and what is the principle upon which 

 its course was decided. 



Here again I found circumstances which induced me to 

 suppose it probable, that it neither turned back to the north, 

 nor mingled with the air which came from the region of the 

 SE. trades, ascended, and then flowed indiscriminately to the 

 north or the south. 



But I saw reasons for supposing that what came to the 

 equatorial calms as NE. trade winds, continued to the south 

 as an upper current ; and that what had come to the same 

 zone as SE. trade winds, ascended and continued over into 

 the northern hemisphere as an upper current, bound for the 

 calm zone of Cancer. 



And these are the principal reasons upon which this sup- 

 position was based. 



At the seasons of the year when the sun is evaporating 

 most rapidly in the southern hemisphere, the most rain is 

 falling in the northern. Therefore I supposed that much of 

 the vapour which is taken up there is precipitated here. 



The evaporating surface in the southern hemisphere is 

 greater, much greater than that in the northern : still all the 

 great rivers are in the northern hemisphere, — the Amazon 

 being regarded as common to both. And this, as far as it 

 goes, is corroborative of the above. 



Independently of other sources of information, the charts 

 taught me to believe that the mean temperature of the tropical 

 regions was higher in the northern than in the southern he- 

 misphere ; for they shew that the difference is such as to 

 draw the equatorial edge of the SE. trades far over on this 

 side of the equator, and to give them force enough to keep 



VOL. LI. NO. CII. — OCTOBER 1851. T 



