140 THE PHYSICAL GEOGRAPHY OF THE SEA. 



our fair-weather winds ; we seldom have rain from the southwest." 

 Buffalo may get much of its rain from the Gulf Stream with east- 

 erly winds. But I speak of the Mississippi Valley ; all the re- 

 spondents there, with the exception of one in Missouri, said, " The 

 southwest winds bring us our rains." 



365. These winds certainly can not get their vapors from the 

 E,ocky ^lountains, 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. 



366. These winds, that feed the sources of the Mississippi with 

 rain, like those between the same parallels upon the ocean, are go- 

 ing from a higher to a lower temperature ; and these winds in the 

 Mississippi Valley, not being in contact with the ocean, or with 

 any other evaporating surface to supply them with moisture, must 

 bring with them from some sea or another that which they deposit. 



367. Therefore, though it may be urged, inasmuch as the winds 

 which brought the rains to Patagonia (§ 344) came direct from the 

 sea, that they therefore took up their vapors as they came along, 

 yet it can not be so urged in this case ; and if these winds could 

 pass with their vapors from the equatorial calms through the upper 

 regions of the atmosphere to the calms of Cancer, and then as 

 surface winds into the Mississippi Valley, it was not perceived 

 why the Patagonian rain winds should not bring their moisture by 

 a similar route. These last are from the northwest, from warmer 

 to colder latitudes ; therefore, being once charged with vapors, 

 they must precipitate as they go, and take up less moisture than 

 they deposit. The circumstance that the rainy season in the Mis- 

 sissippi Valley (§ 330) alternates with the dry season on the coast 

 of California and Oregon, indicates that the two regions derive 

 vapor for their rains from the same fountains. 



368. This, however, could be regarded only as circumstantial 

 evidence. Not a fact had yet been elicited to prove that the 

 course of atmospherical circulation suggested by my investiga- 

 tions is the actual course in nature. It is a case in which I could 

 yet hope for nothing more direct than such conclusions as might 

 legitimately flow from circumstances. 



