48 IMPERFECTION OF THE [Chap. X. 



CHAPTEE X. 

 On the Imperfection of the Geological Record. 



On the absence of intermediate varieties at the present day — On 

 the nature of extinct intermediate varieties ; on their number — 

 On the lapse of time, as inferred from the rate of denudation 

 and of deposition — On the lapse of time as estimated by years 

 — On the poorness of our palceontological collections — On the 

 intermittence of geological formations — On the denudation of 

 granitic areas — On the absence of intermediate varieties in any 

 one formation — On the sudden aj3pearance of groups of species — - 

 On their sudden appearance in the lowest known fossiliferous 

 strata — Antiquity of the habitable earth. 



In the sixth chapter I enumerated the chief objections 

 which might be justly urged against the views main- 

 tained in this volume. Most of them have now been 

 discussed. One, namely the distinctness of specific 

 forms, and their not being blended together by innumer- 

 able transitional links, is a very obvious difficulty. I 

 assigned reasons why such links do not commonly occur 

 at the present day under the circumstances apparently 

 most favourable for their presence, namely on an 

 extensive and continuous area with graduated physical 

 conditions. I endeavoured to show, that the life of 

 each species depends in a more important manner on 

 the presence of other already defined organic forms, 

 than on climate, and, therefore, that the really governing 

 conditions of life do not graduate away quite insensibly 

 like heat or moisture. I endeavoured, also, to show 



