EASTING OF THE TRADE- WINDS, ETC. 165 



those calm belts from difterent directions, crossing over, each in its 

 proper direction, without mingling. 



357. The same process of reasoning which conducted us (§ 355) 

 The rain winds ill the into the tradc-wiud Tcgion of the northern hemi- 

 jiississippi Valley, gphero for the sources of the Patagonian rains, now 

 invites us into the trade-wind regions of the South Pacific Ocean 

 to look for the vapour siblings of the Mississippi. If the rain ^™ds 

 of the Mississippi Yalley come from the east, then we should have 

 reason to suppose that their vapours were taken up from the 

 Atlantic Ocean and Gulf Stream ; if the rain wmds come from the 

 south, then the vapom' springs might, perhaps, be in the Gulf of 

 Mexico ; if the rain winds come h'om the north, then the great 

 lakes might be supposed to feed the air with moisture for the 

 fountains of that river ; but if the rains come from the west, where, 

 short of the great Pacific Ocean, should we look for the place of 

 evaporation ? AVondering where, I addressed a circidar letter to 

 farmers and planters of the Mississippi Yalley, requesting to be 

 informed as to the direction of their rain mnds. I received replies 

 from Virginia, Mississippi, Temiessee, Missouri, Indiana, and Ohio ; 

 and subsequently, from Colonel W. A. Bird, Bufialo, New York, 

 who says, " The south-west winds are our fair-weather winds ; we 

 seldom have rain from the south-west." Buffalo may get much of 

 its rain from the Gulf Stream with easterly winds. But I speak 

 of the Mississippi valley ; all the respondents there, Avith the 

 exception of one in Missomi, said, " The south-west winds bring us 

 om* rains." These muds certainly cannot get their vapoiurs from 

 the Eocky Mountains, nor from the Salt Lake, for they rain quite 

 as much upon that basin as they evaporate from it again ; if they 

 did not, they would in the process of time have evaporated all the 

 water there, and the lake would now be dry. These winds, that 

 feed the sources of the Mississippi with rain, like those between the 

 same parallels upon the ocean, are going from a higher to a lower 

 temperatm^e ; and the winds in the Mississippi valley, not being in 

 contact with the ocean, or with any other evaporating surface to 

 supply them with moistm^e, must bring with them from some sea 

 or another that which they deposit. Therefore, though it may be 

 urged, inasmuch as the winds which brought the rains to Patagonia 

 (§ 355) came direct from the sea, that they therefore took up 

 their vapom-s as they came along, yet it cannot be so urged in this 

 case ; and if these winds could pass with their vapom's fi'om the 

 equatorial calms through the upper regions of the atmosphere to 



