48 IMPERFECTION OP THE [Chap. X. 



CHAPTEE X. 



ON THE IMPERFECTION OF THE GEOLOGICAL BECOBD. 



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 palaeontological 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 appearance 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 objec- 

 tions which might be justly urged against the views 

 maintained in this volume. Most of them have now 

 been discussed. One, namely the distinctness of spe- 

 cific forms, and their not being blended together by in- 

 numerable transitional links, is a very obvious difficulty. 

 I assigned reasons why such hnks do not commonly oc- 

 cur at the present day under the circumstances ap- 

 parently most favourable for their presence, namely, on 

 an extensive and continuous area with graduated phys- 

 ical 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 cUmate, and, therefore, that the really govern- 

 ing conditions of life do not graduate away quite insen- 

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



