OF ORGANIC NATURE. 41 



you for the purpose of raising a paradoxical difficulty ; 

 the fact is, that the great mass of deposits have taken 

 place in sea-bottoms which are gradually sinking, and 

 have been formed under the very conditions I am here 

 supposing. 



Do not run awaj 7 witli the notion that this subverts 

 the principle I laid down at first. The error lies in 

 extending a principle which is perfectly applicable to 

 deposits in the same vertical line to deposits which are 

 not in that relation to one another. 



It is in consequence of circumstances of this kind, and 

 of others that I might mention to you, that our con- 

 clusions on and interpretations of the record are really 

 and strictly only valid so long as we confine ourselves 

 to one vertical section. I do not mean to tell vou that 

 there are no qualifying circumstances, so that, even 

 in very considerable areas, we may safely speak of 

 conformably superimposed beds being older or younger 

 than others at many different points. But we can 

 never be quite sure in coming to that conclusion, 

 and especially we cannot be sure if there is any 

 break in their continuity, or any very great distance 

 between the points to be compared. 



Well now, so much for the record itself, — so much 

 for its imperfections, — so much for the conditions to be 

 observed in interpreting it, and its chronological indi- 

 cations, the moment we pass beyond the limits of a 

 vertical linear section. 



Now let us pass from the record to that which it 

 contains, — from the book itself to the writing and the 

 figures on its pages. This writing and these figures 

 consist of remains of animals and plants which, in the 



