MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 129 



plied with vapor enough to feed the great rivers, and supply the 

 rains for the whole earth between us and the north pole. In this 

 case, we should have an evaporating region on the north as well 

 as on the south side of this zone of Cancer ; hut investigation 

 shows no such region ; I speak exclusively of the ocean. 



313. Hence it was inferred that A and G do come out on the 

 surface as represented by Plate I. But what is the agent that 

 should lead them out by such opposite paths ? 



314. According to this mode of reasoning, the vapors which 

 supply the rains for H would be taken up in the southeast trade- 

 wind region by F, and conveyed thence along the route G to H. 

 And if this mode of reasoning be admitted as plausible — if it be 

 true that G have the vapor which, by condensation, is to water 

 with showers the extra-tropical regions of the northern hemisphere, 

 Nature, we may be sure, has provided a guide for conducting G 

 across this belt of calms, and for sending it on in the right way. 

 Here it was, then, at this crossing of the winds, that I thought I 

 first saw the foot-prints of an agent whose character I could not 

 comprehend. Could it be the magnetism that resides in the oxy- 

 gen of the air ? 



315. Heat and cold, the early and the latter rain, clouds and 

 sunshine, are not, we may rely upon it, distributed over the earth 

 by chance ; they are distributed in obedience to laws that are as 

 certain and as snre in their operations as the seasons in their 

 rounds. If it depended upon chance whether the dry air should 

 come out on this side or on that of this calm belt, or whether the 

 moist air should return or not whence it came — if such were the 

 case in nature, we perceive that, so far from any regularity as to 

 seasons, we should have, or might have, years of droughts the 

 most excessive, and then again seasons of rains the most destruct- 

 ive ; but, so far from this, we find for each place a mean annual 

 proportion of both, and that so regulated withal, that year after 

 year the quantity is preserved with remarkable regularity. 



316. Having thus shown that there is no reason for supposing 

 that the upper currents of air, when they meet over the calms of 

 Cancer and Capricorn, are turned back to the equator, but having 

 shown that there is reason for supposing that the air of each cur- 



