MAGNETISM AND CIRCULATION OF THE ATMOSPHERE. 117 



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. 



216. This was circumstantial evidence. No fact had yet been 

 elicited to prove that the course of atmospherical circulation sug- 

 gested by my investigations 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. 



My friend Lieutenant De Haven v/as about to sail in command 

 of the American Arctic Expedition in search of Sir John Frank- 

 lin. 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 by w^hich we have been seeking to enter into the chambers 

 of the wind, and to '^ tell whence it cometh and w^iither it goeth." 



It is not for man to follow the '' wind in his circuits ;" and all 

 that could be hoped was, after a close examination of all the facts 

 and circumstances w^hich 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 estabhshed a 

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

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

 investigations to confirm or set aside- 



217. 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 (§ 216). 



That celebrated microscopist reports that he found South Amer- 

 ican infusoria in the blood-rains and sea-dust of the Cape Verd 

 Islands — Lyons, Genoa, and other places (^ 158). 



Thus confirming, as far as such evidence can, the indications 

 of our observations, and increasing the probability that the general 

 course of atmospherical circulation is in conformity with the sug- 



