LITE Di BEES'E. 73 



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 America. 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 obscurity 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 direc- 

 tion. 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 difiusion 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 cal- 

 cined 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 them- 

 selves, by myriads, in brine so strong as to contain two 

 pounds of salt to the gallon ? A solution so concentrated 

 is suflScient in general to destroy all life.-f* Yet, in the 



* Naturalist's Voyage, chap. L 



t Goadby's preservative fluid contains but three-quarters of a pound 

 of salts to a gallon of water. 



