THEORY OF THE EARTH. 75 



serts which occupy the middle of Africa, Asia, the 

 two Americas, and New Holland. But, if we care- 

 fully attend to the kinds of quadrupeds that have 

 been recently discovered, and to the circumstances 

 of their discovery, we shall easily perceive that 

 there is very little chance indeed of our ever find- 

 ing alive those which have only been seen in a 

 fossil state. 



Islands of moderate size, and at a considerable 

 distance from the large continents, have very few 

 quadrupeds, and these mostly very small. When 

 they contain any of the larger quadrupeds, these 

 must have been carried to them from other coun- 

 tries. Cook and Bougainville found no other quad- 

 rupeds besides hogs and dogs in the South Sea 

 islands ; and the largest quadruped of the West 

 India islands, when first discovered, was the agouti, 

 a species of the cavy, an animal apparently between 

 the rat and the rabbit, 



It is true, that the great continents, as Asia, Afri- 

 ca, the two Americas, and New Holland, have 

 large quadrupeds, and, generally speaking, con- 

 taip species proper to each : Insomuch, that, upon 

 discovering countries which are isolated from the 

 rest of the world, the animals they contain of the 

 class of quadrupeds were found entirely different 

 from those which existed in other countries. Thus, 

 when the Spaniards first penetrated into South 

 America, they did not find it to contain a single 





