viii 



fluence on the forms and the habits of or- 

 ganized beings. In proportion to the breadth 

 of the continents, the greater is the display 

 on the surface of the soil, of the richness of 

 the animal and vegetable productions ; the 

 more distant the central chain of moun- 

 tains from the shores of the ocean, the 

 greater variety we find, in the bosom of the 

 earth, of those stony strata, the regular 

 succession of which unfolds to us the his- 

 tory of our planet. In the same manner, 

 as every being considered apart is im- 

 pressed with a particular type, we find the 

 same impression in the arrangement of 

 brute matter organized in rocks, in the dis- 

 tribution and mutual relations of plants 

 and animals. The great problem of the 

 physical description of the globe, is the 

 determination of the form of these types, 

 the laws of their relations with each other, 

 and the eternal ties which link the phe- 

 nomena of life, and those of inanimate na- 

 ture. 



In explaining the motives which en- 

 gaged me to undertake an expedition into 

 the interior of a continent, I merely state 

 the general direction of my ideas at an age 



