OF ORGANIC NATURE. 41 



is carried no farther than a, forming the bed A 1 , and 

 the coarse no farther than b, forming the bed B 1 , the 

 result will be the formation of two continuous beds, 

 one of fine sediment (AA 1 ) over-lapping another of 

 coarse sediment (BB 1 ). Now suppose the whole sea- 

 bottom is raised up, and a section exposed about the 

 point A 1 ; no doubt, at this spot, the upper bed is 

 younger than the lower. But we should obviously 

 greatly err if we concluded that the mass of the upper 

 bed at A was younger than the lower bed at B ; for 

 we have just seen that they are contemporaneous de- 

 posits. Still more should we be in error if we supposed 

 the upper bed at A to be younger than the continu- 

 ation of the lower bed at B 1 ; for A was deposited long 

 before B 1 . In fine, if, instead of comparing imme- 

 diately adjacent parts of two beds, one of which lies 

 upon another, we compare distant parts, it is quite pos- 

 sible 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 Kes 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 



