APPLICATIONS OF THE MICROSCOPE. 139 



east trade-wind region of South America ! 

 Professor Ehrenberg has examined specimens 

 of sea-dust from the Cape de Verd Islands and 

 neighbourhood, from Malta, Genoa, Lyons, and 

 the Tyrol. Their similarity is as striking as if 

 all the specimens had been taken from the same 

 pile. Every specimen is found to consist chiefly 

 of South American forms. How could the wind 

 carry them from South America along this track ? 

 Mark the prevailing course of the north-east 

 trade-wind along the surface over all this direc- 

 tion. It might carry dust to South America 

 it could not possibly carry any from it. The 

 many feathered arrows in Maury's Plate (vui.) 

 show at a glance, how strongly and steadily the 

 north-east trades bear down on South America 

 to the south of the Calms of Cancer. But the 

 supposed course of the south-east trades after 

 they cross the equator, and as they travel north- 

 ward, would carry the South American organ- 

 isms directly along all the course in which they 

 have been found the Cape de Verd Islands, 

 Lyons, Genoa, Switzerland, the Tyrol. For 

 proof, turn again to Maury's Plates (vn. and 

 vui.) ; observe how the feathered arrows fly 



