DISCREPANCIES. 



wind whenever it has fallen, and from its having 

 always fallen during those months when the har- 

 mattan is known to raise clouds of dust high into 

 the atmosphere, we may feel sure that it all comes 

 from Africa. It is, however, a very singular fact, 

 that, although Professor Ehrenberg knows many 

 species of infusoria peculiar to Africa, he finds 

 none of these in the dust which I sent him ; on 

 the other hand, he finds in it two species which 

 hitherto he knows as living only in South Amer- 

 ica. This dust falls in such quantities as to dirty 

 everything on board, and to hurt people's eyes; 

 vessels even have run on shore owing to the ob- 

 scurity of the atmosphere. It has often fallen on 

 ships when several hundred, and even more than 

 a thousand miles from the coast of Africa, and at 

 points sixteen hundred miles distant in a north 

 and south direction. In some dust which was 

 collected on a vessel three hundred miles from the 

 land, I was much surprised to find particles of 

 stone, about the thousandth of an inch square, 

 mixed with finer matter. After this fact, one 

 need not be surprised at the diffusion of the 

 far lighter and smaller sporules of cryptogamic 

 plants."* 



In all these situations, in which we have seen 

 organic existence maintained, we must admit that 

 there is nothing actually hostile to life. The 

 snow, the hot sand, the calcined lava, the dust, 

 seem ungenial spheres for living beings, offer but 

 little encouragement to them, as we should have 

 supposed, but are not actually destructive. What 

 shall we say, however, to animals disporting 

 themselves, by myriads, in brine so strong as to 

 contain two pounds of salt to the gallon? A 

 solution so concentrated is sufficient in general to 



* "Naturalist's Voyage," chap. i. 

 75 



