278 Lieut. Maury on the Probable Relation between 



the NE. trade winds out of the southern hemisphere almost 

 entirely. 



Consequently, as before stated, the SE. trade winds being 

 in contact with a more extended evaporating surface, and 

 continuing in contact with it for a longer time or through a 

 greater distance, they would probably arrive at the trade 

 wind place of meeting, more heavily laden with moisture than 

 the others. 



Taking the laws and rate of evaporation into consideration, 

 I could find no part of the ocean of the northern hemisphere 

 from which, according to the indications of the charts, the 

 sources of the Mississippi, the St Lawrence, and the other 

 great rivers of our hemisphere could be supplied. 



It appeared to me,.therefore, that the extra- tropical regions 

 of the northern hemisphere stood in the relation of a condenser 

 to a grand steam machine, the boiler of which was in the 

 region of the SE. trade winds, and that the trade winds of 

 this hemisphere performed the like office for the regions be- 

 yond Capricorn. 



The calm zone of Capricorn is the duplicate of that of 

 Cancer, and the winds flow from it as they do from that : both 

 north and south : with this difference, that on the polar side 

 of the Capricorn belt they prevail from the NW. instead of 

 the SW., and on the equatorial side from the SE., instead 

 ofNE. 



Now if it were so, that the vapour of the NE. trade winds 

 were condensed in the extra-tropical regions of the southern 

 hemisphere, the following path, on account of the effect of 

 diurnal rotation of the earth upon the course of the winds, 

 would represent the mean circuit of a portion of the atmo- 

 sphere moving according to the general system of its circu- 

 lation over the Pacific ocean, viz. : coming down from the 

 north as an upper current, and appearing on the surface of 

 the earth in about longitude 130° W., and near the tropic of 

 Cancer, it would here commence to blow the NE. trade winds 

 of that region. 



Its course would be towards the equator somewhat in the 

 direction of the King's Mill group of islands. Meeting no 

 land in this long oblique track over the tepid waters of a 



