Brongniart on Fossil Organic Remains. 227 
particular sum of resemblance to one another, and a general 
sum of difference with the deposits above and below it. It has 
also been thought, that this last sum becomes so much the 
higher, or the difference so much the greater, in proportion as 
these deposits are more distinct or more removed from one an- 
other in a vertical direction. This rule, which was at first 
cautiously assumed, and only for certain localities (as should al- 
ways be done with the establishment of laws, which can only 
result from the observation of a great number of facts), has 
been found applicable to almost all the places observed in the 
different parts of the globe, and to all the remains of organised 
bodies buried in its beds, whether they belong to the class of 
animals or to that of vegetables. To the present time, the ex- 
ceptions which appear to have presented themselves have vanish- 
ed under a more scrupulous examination, or are explained by 
the discovery of particular circumstances which have given rise 
to them. Thus, on reducing this rule to the general exposition 
which we have made, it does not appear liable to any real 
objection, and all geologists are now agreed in thinking, that 
the generations of organised bodies which have successively 
inhabited the surface of the earth, differ from the present gene- 
ration in proportion as their debris are farther removed from 
the surface of the earth, or, which nearly comes to the same 
thing, in proportion as the periods at which they have lived are 
more remote from the present time. It follows from the same 
rule, that this distinct succession of generations would present 
itself only in the structure of the crust of the globe. It would 
also of itself be sufficient to establish the fact, as has been re- 
marked by M. Cuvier, that this crust has not been formed by a 
single operation. But this character of succession in the for- 
mation of the beds of the earth, is frequently associated with 
other very remarkable differences, such as the nature of rocks,, 
their structure in the great, their known order of superposition, 
the minerals which accompany them, &c. Now, these mineralogf- 
cal circumstances are almost always found in agreement with the 
characters which are taken from the general resemblance of or- 
ganised bodies in deposits, considered as of the same formation 
from their geognostical characters; and they are also pretty 
