MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 141 



369. My friend Lieutenant De Haven was about to sail in com- 

 mand of the American Arctic Expedition in search of Sir John 

 Franklin. Infusoria are sometimes found in sea-dust, rain-drops, 

 hail-stones, or snow-flakes ; and if by any chance it should so 

 turn out that the locus of any of the microscopic infusoria which 

 might be found descending with the precipitation of the Arctic 

 regions should be identified as belonging to the regions of the 

 southeast trade-winds, we should thus add somewhat to the 

 strength of the many clews oj which we have been seeking to 

 enter into the chambers of the wind, and to " tell whence it com- 

 eth and whither it goeth." 



370. It is not for man to follow the "wind in his circuits;" 

 and aU that could be hoped was, after a close examination of all 

 the facts and circumstances which these researches upon the sea 

 have placed within my reach, to point out that course which seemed 

 to be most in accordance with them ; and then, having established 

 a probability, or even a possibility, as to the true course of the 

 atmospheric circulation, to make it known, and leave it for future 

 investigations to confirm or set aside. 



371. 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 clew which I hoped, almost against hope, De 

 Haven would place in my hands (§ 369) from the north pole. 



372. 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 (§ 273). 



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

 tions of our observations, and increasing the probability that the 

 general course of atmospherical Circulation is in conformity with 

 the suggestions of the facts gathered from the sea as I had inter- 

 preted them, viz., that the trade-winds of the southern hemisphere, 

 after arriving at the belt of equatorial calms, ascend and continue 

 in their course toward the calms of Cancer as an upper current 

 from the southwest, and that, after passing this zone of calms, 

 they are felt on the surface as the prevailing southwest winds of 

 the extra-tropical parts of our hemisphere ; and that, for the most 



