MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 121 



these polar calms by a circular or spiral motion, traveling in the 

 northern hemisphere against, and in the southern with the hands 

 of a watch. The circular gales of the northern hemisphere are 

 said also to revolve in like manner against the hands of a watch, 

 while those in the southern hemisphere travel the other way. 

 Now, should not this discovery of these three poles, this coinci- 

 dence of revolving winds, with the other circumstances that have 

 been brought to light, encourage us to look to the magnetism of 

 the air for the key to these mysterious but striking coincidences ? 

 Indeed, so wide for speculation is the field presented by these 

 discoveries, that we may in some respects regard this great globe 

 itself, with its " cups" and spiral wires of air, earth, and water, as 

 an immense " pile" and helix, w^hich, being excited by the natural 

 batteries in the sea and atmosphere of the tropics, excites in turn 

 its oxygen, and imparts to atmospherical matter the properties of 

 magnetism. 



225. With the lights which these discoveries cast, we see (Plate 

 I.) why air, which has completed its circuit to the whirl* about the 

 Antarctic regions, should then, according to the laws of magnet- 

 ism, be repelled from the south, and attracted by the opposite pole 

 toward the north. 



And when the southeast and the northeast trade-winds meet in 

 the equatorial calms of the Pacific, would not these magnetic 

 forces be sufficient to determine the course of each current, bring- 

 ing the former, with its vapors of the southern hemisphere, over 

 into this, by the courses already suggested ? 



226. This force and the heat of the sun would propel it to the 

 north. The diurnal rotation of the earth propels it to the east ; 

 consequently, its course, first through the upper regions of the 

 atmosphere, and then on the surface of the earth, after being 

 conducted by this newly-discovered agent across the calms of 

 Cancer, would he from the southward and westw^ard to the north- 

 ward and eastward. 



These are the winds (§ 122) which, on their w^ay to the north 

 from the South Pacific, would pass over the Mississippi Valley, 

 and they appear (^214) to be the rain winds there. Whence, then, 

 if not from the trade-wind regions of the South Pacific, can the 

 vapors for those rains come ? 



* " It whirleth about contimaally.'" — Bible. 



