SYSTEM OF NATURE. 
125 
the earth is covered by numerous layers of stratified rocks, 
reposing one on the other in an order strictly according 
with the eras of their deposition. As far as research has 
hitherto extended, the lowermost of these layers or strata 
contain no remains of organized life: hence it appears that 
during the process of their deposition, a period extending 
perhaps to innumerable ages, the Creator had not peopled 
the earth with living inhabitants. Almost every one of the 
remaining strata contains the relics of certain animals 
absent from the strata next in succession both above and 
below it: and from this circumstance, combined with a 
consideration of the time required for the deposition of 
each stratum, the inference has been fairly drawn, that 
living beings have been called into existence, and have 
become utterly extinct, at a great number of periods so re¬ 
mote from each other, that we can find no available key to 
the mensuration of intervening time. Hence we learn that 
our former knowledge of Zoology, instead of making any 
claims to be considered as general, was confined to a por¬ 
tion of a series perpetually changing—was in fact restricted 
to the instant of time serving to couple the future with 
the past. 
It becomes a matter of intense interest to the zoologist 
to compare the forms composing these preadamite crea¬ 
tions with those which are still moving around and among 
us, synchronous in creation and existence with our own. 
It has been the peculiar object of the geologist to make 
this comparison: to search laboriously into the sublime 
records of the past: to reconstruct perfect frames from 
bones or shells, and even from their fragments, when bro¬ 
ken, crushed, and widely separated from each other: to 
clothe the frames with muscle and endow them with life— 
