MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 105 



winds discharge into the equatorial calm belt continues to go 

 south, as an upper current bound for the calms of Capricorn. 

 But what should cause this wind to cross over ? Why should there 

 not be a general mingling in this calm belt of the air brought by 

 the two trade-w^inds, and why should not that which the southeast 

 winds convey there be left, after its ascent, to flow off either to 

 the north or to the south, as chance directs ? 



175. In the first place, it was at variance with my belief in the 

 grand design ; for I could not bring myself to believe that the 

 operations of such an important machine as the atmosphere should 

 be left to chance, even for a moment. Yet I knew of no agent 

 which should guide the wind across these calm belts, and lead it 

 out always on the side opposite to that on which it entered ; nev- 

 ertheless, certain circumstances seemed to indicate that such a 

 crossing does take place. 



176. Evidence in favor of it seemed to be afforded by this cir- 

 cumstance, viz., our researches enabled us to trace from the belt 

 of calms, near the tropic of Cancer, which extends entirely across 

 the seas, an efflux of air both to the north and to the south ; from 

 the south side of this belt the air flows in a never-ceasing breeze, 

 called the northeast trade-winds, toward the equator. (Plate I.) 



On the north side of it, the prevailing winds come from it also, 

 but they go toward the northeast. They are the well-known 

 southw-esterly winds which prevail along the route from this 

 country to England, in the ratio of two to one. But why should 

 we suppose a crossing to take place here ? 



177. We suppose so, because these last-named winds are going 

 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 than evaporation. 



178. But where, it may be asked, does the vapor which these 

 W'inds carry along, for the replenishing 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 north- 

 east trades. They 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 saturated with moisture. Thus circumstances again 

 pointed to the southeast trade-wind regions as the place of supply. 



