146 THE PHYSICAL GEOGRAPHY OF THE SEA. 



389. These are the winds (§ 181) which, on their way to the 

 north from the South Pacific, would pass over the Mississippi 

 Valley, and they appear (§ 364) to be the rain winds there. 

 Whence, then, if not from the trade-wind regions of the South 

 Pacific, can the vapors for those rains come ? 



390. According to this view, and not taking into account any 

 of the exceptions produced by the land and other circumstances 

 upon the general circulation of the atmosphere over the ocean, the 

 southeast trade-winds, which reach the shores of Brazil near the 

 parallel of E,io, and which blow thence for the most part over the 

 land, should be the winds which, in the general course of circula- 

 tion, would be carried, after crossing the Andes and rising up in 

 the belt of equatorial calms, toward Northern Africa, Spain, and 

 the South of Europe. 



391. They might carry with them the infusoria of Ehrenberg 

 (§ 273), but, according to this theory, they would be wanting in 

 moisture. ISTow, are not those portions of the Old World, for the 

 most part dry countries, receiving but a small amount of precipi- 

 tation ? ^ 



392. Hence the general rule: those countries to the north of 

 the calms of Cancer, which have large bodies of land situated to 

 the southward and westward of them, in the southeast trade-wind 

 region of the earth, should have a scanty supply of rain, and vice 

 versa. 



393. Let ug. try this rule : The extra-tropical part of New Hol- 

 land comprises a portion of land thus situated in the southern hem- 

 isphere. Tropical India is to the northward and westward of it ; 

 and tropical India is in the northeast trade-wind region, and should 

 give extra-tropical New HoUard a slender supply of rain. But 

 what modifications the monsoons of the Indian Ocean may make 

 to this rule, or what effect they may have upon the rains in New 

 Holland, my investigations in that part of the ocean have not been 

 carried far enough for final decision ; though New Holland is a dry 

 country. Referring back to p. 84 for what has been already said 

 concerning the " Meteoeological Agencies" (§ 159) of the at- 

 mosphere, it will be observed that cases are there brought forward 

 which afford trials for this rule, every one of which holds good. 



