Magnetism and the Trade Winds. 285 



It was at this stage of the matter* that my friend Baron 

 von Gerolt, the Prussian minister, had the kindness to place 

 in my hand Ehrenberg's work, " Passat — Staub und Blut — 

 Regen." 



Here I found the cluet which I hoped, almost against 

 hope, De Haven would place in my hands. 



That celebrated microscopist reports that he found South 

 American infusoria in the blood-rains, and sea-dust of the 

 Cape Verd Islands, — Lyons, Genoa, and other places. J 



Thus confirming, as far as such evidence can, the indica- 

 tions of the " Wind and Current Charts," and increasing the 

 probability that the general course of atmospherical circula- 

 tion is in conformity with the suggestions of the charts as I 

 had interpreted them, viz.: that the trade winds of the south- 

 ern hemisphere, after arriving at the belt of equatorial calms, 

 ascend and continue in their course towards the calms of 

 Cancer as an upper current from the SW., and that after 

 passing this zone of calms, they are felt on the surface as 

 the prevailing SW. winds of the extra-tropical parts of our 

 hemisphere ; and that for the most part they bring their 

 moisture with them from the trade- wind regions of the oppo- 

 site hemisphere. 



Continuing on towards the North Pole from the SW., they 

 enter the Arctic regions on a spiral curve, continually lessen- 

 ing the gyrations until, whirling about in a direction contrary 

 to the hands of a rcatch, this air ascends and commences its 

 return as an upper current towards the calms of Cancer. 



It returns to this zone from the opposite direction, NE., 

 by which it approached the pole. 



The atmosphere in this part of the circuit is moving in the 

 direction called s' in a previous part of this paper. 



Arrived at the calms of Cancer, s' meets 8" in the upper 

 regions of the atmosphere. 



They both descend — and the fact that the barometer stands 

 higher here§ than upon any other parallel, shews that here 



wr * See my letter to him, paper F ; also, paper read by me before the Ameri- 



^L can Association at its meeting in Charleston, March 1850. 

 Hft t Vide paper F. + Vide paper G, " Passat— Staub, &c.,"' p.— 



^K § Humboldt. 



L 



