138 THE MICROSCOPE. 



had been brought. " If by any chance it should 

 turn out that the locus of any of the microscopic 

 i Infusoria/ so falling, could be identified as 

 belonging to regions travelled by the south-east 

 trade-winds in their hypothetical northern 

 course, strength would be added to many " clews 

 which conduct us into the chambers of the wind, 

 and tell whence it coineth, and whither it goeth." 

 In a previous page we have called attention 

 to Ehrenberg's Passat-Staub und Blut-Regen, 

 and showed how microscopic infusoria, certainly 

 originally belonging to South America, have 

 fallen from the heavens along the western shores 

 of Africa, and the northern shores of the Medi- 

 terranean sea. 1 Maury observes that seamen 

 tell us of " red fog," which they occasionally 

 encounter, especially near the Cape de Verd 

 Islands. Elsewhere they meet showers of dust. 

 The Mediterranean precipitation has been called 

 " Sirocco dust," or " African dust," because sup- 

 posed to come from the deserts of Africa. But 

 this dust, when microscopically examined, is 

 found to consist of organisms whose habitat is 

 not Africa, lout South America, and in the south- 



1 See p. 64. 



