BOOK VII. 



THE MIGRATIONS OF ANIMALS. 



MANY animals, impelled by imperious demands, or by an 

 instinctive irresistible force, quit their habitual residence 

 at a certain time, and direct their way to distant regions. 

 Such migrations, the object of which eludes our observa- 

 tion, are noticed in nearly all classes of the animal king- 

 dom. Usually they are seen to take place periodically, but 

 at other times they only occur, as it were, accidentally, and 

 all at once astonish the inhabitants of the countries which 

 are the theatre of them, and into which the unexpected in- 

 vaders carry sometimes devastation, famine, and death. 



At other times it is violence that compels legions of ani- 

 mals to quit the place where they had established them- 

 selves. In the countries where man does not decimate 

 them, they swarm in such abundance, and are so crowded 

 together, that one can scarcely understand how they exist ; 

 their numbers are alarming. The pictures that Livingstone 

 has drawn of the exuberance of game in wild districts of 

 Central Africa, and in particular on the banks of the Zam- 

 besi, suffice to give us an idea of the fecundity of nature. 

 But this very fecundity is fatal to the weak tribes ; the 

 stronger ones, getting the upper hand, drive them away or 



