154 THE PHYSICAL GEOGRAPHY OF THE SEA. 



tation is in excess of evaporation, and because at sea they are go- 

 ing from a warmer to a colder climate, and therefore it may be in- 

 ferred that nature exacts from them what we know she exacts 

 from the air under similar circumstances, but on a smaller scale, 

 before our eyes, viz., more precipitation at sea than evaporation. 

 In other words, they probably leave in the Atlantic as much vapor 

 as they take up from the Atlantic. Then where, it may be asked, 

 does the vapor which these winds carry along, for the replenish- 

 ing of the whole extra-tropical regions of the north, come from ? 

 They did not get it as they came along in the upper regions, a 

 counter-current to the northeast trades, unless they evaporated the 

 trade-wind clouds, and so robbed those winds of their vapor. They 

 certainly did not get it from the surface of the sea in the calm belt 

 of Cancer, for they did not tarry long enough there to become sat- 

 urated with moisture. Thus circumstances again pointed to the 

 southeast trade-wind regions as the place of supply. This ques- 

 tion has been fully discussed in Chapter V., where it has been 

 shown they did not get it from the Atlantic. Moreover, these re- 

 searches afforded grounds for the supposition that the air of which 

 the northeast trade-winds are composed, and which comes out of 

 the same zone of calms as do these southwesterly winds, so far from 

 being saturated with vapor at its exodus, is dry ; for near their po- 

 lar edge, the northeast trade-winds are, for the most part, dry winds. 

 850. Facts seem to confirm this, and the calm belts of Cancer 

 Wet and diy air of ^^^ Capricom both throw a flood of light upon the 

 the calm belts. subjcct. Thcsc are two bauds of light airs, calms, 

 and baffling winds, which extend entirely around the earth. The 

 air flows out north and south from these belts. That which comes 

 out on the equatorial side goes to feed the trades, and makes a dry 

 wind ; that which flows out on the polar side goes to feed the 

 counter-trades (§ 349), and is a rain wind. How is it that we can 

 have from the same trough or receiver, as these calm belts may 

 be called, an efflux of dry air on one side and of moist on the 

 other? Answer : upon the supposition that the air without rain 

 comes from one quarter, that with rain from another — that, com- 

 ing from opposite directions to this place of meeting, where there 

 is a crossing, they pass each other in their circuits. They both 

 meet here as upper currents, and how could there be a crossing 

 without an agent or influence to guide them ? and why should wo 



