260 ON THE ORIGIN OF SPECIES 



other parts of the world. The most skilful geologist, if 

 his attention had been exclusively confined to these 

 large territories, would never have suspected that 

 during the periods which were blank and barren in his 

 own country, great piles of sediment, charged with 

 new and peculiar forms of life, had elsewhere been 

 accumulated. And if in each separate territory, hardly 

 any idea can be formed of the length of time which has 

 elapsed between the consecutive formations, we may 

 infer that this could nowhere be ascertained. The 

 frequent and great changes in the mineralogical com- 

 position of consecutive formations, generally implying 

 great changes in the geography of the surrounding 

 lands, whence the sediment has been derived, accords 

 with the belief of vast intervals of time having elapsed 

 between each formation. 



But we can, I think, see why the geological forma- 

 tions of each region are almost invariably intermittent ; 

 that is, have not followed each other in close sequence. 

 Scarcely any fact struck me more when examining 

 many hundred miles of the South American coasts, 

 which have been upraised several hundred feet within 

 the recent period, than the absence of any recent 

 deposits sufficiently extensive to last for even a short 

 geological period. Along the whole west coast, which 

 is inhabited by a peculiar marine fauna, tertiary beds 

 are so poorly developed, that no record of several suc- 

 cessive and peculiar marine faunas will probably be 

 preserved to a distant age. A little reflection will ex- 

 plain why along the rising coast of the western side of 

 South America, no extensive formations with recent or 

 tertiary remains can anywhere be found, though the 

 supply of sediment must for ages have been great, 

 from the enormous degradation of the coast-rocks and 

 from muddy streams entering the sea. The explana- 

 tion, no doubt, is, that the littoral and sub-littoral 

 deposits are continually worn away, as soon as they are 

 brought up by the slow and gradual rising of the land 

 within the grinding action of the coast-waves. 



We may, I think, safely conclude that sediment 



