4 
XI PHENOMENA OF ORGANIC NATURE 345 
In fine, if, instead of comparing immediately 
adjacent parts of two beds, one of which les upon 
‘another, we compare distant parts, it is quite 
possible that the upper may be any number of 
years older than the under, and the under any 
number of years younger than the upper. 
Now you must not suppose that I put this 
before 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 away with the notion that this 
‘subverts the principle I laid down at first. The 
error lies in extending a principle which is_per- 
fectly 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 conclusions 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 you that there are no qualifying 
circumstances, so that, even in very considerable 
areas, we may safely speak of conformably super- 
imposed beds being older or younger than others 
at many different points. But we can never be 
“quite sure in coming to that conclusion, and 
ely we cannot be sure if there is any break 
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