THEORY OF THE EARTH. 



able, that it connects natural and civil history in 

 one uninterrupted series. 



When we measure the effects produced in a 

 given time by causes still acting, and compare 

 them with those which the same causes have pro- 

 duced since they have begun to act, we are en- 

 abled to determine nearly the instant at which 

 their action commenced ; which is necessarily the 

 same as that in which our continents assumed 

 their present form, or that of the last sudden re- 

 treat of the waters. 



It must, in fact, have been since this last re- 

 treat of the waters, that our present steep decli- 

 vities have begun to disintegrate, and to form 

 heaps of debris at their bases ; that our present 

 rivers have begun to flow, and to deposit their 

 alluvial matters ; that our present vegetation has 

 begun to extend itself, and to produce soil ; that 

 our present cliffs have begun to be corroded 

 by the sea ; that our present downs have be- 

 gun to be thrown up by the wind: just as it 

 must have been since this same epoch, that co- 

 lonies of men have begun, for the first or second 

 time, to spread themselves, and to form establish- 

 ments in places fitted by nature for their recep- 

 tion. I do not here take the action of volcanoes 

 into account, not only because of the irregula- 

 rity of their eruptions, but because we have no 

 proofs of their not having been able to exist mi- 



