22 ON THE LAW WHICH HAS REGULATED 



they differ considerably in their fossils, and you may 

 then get some notion of how small a portion of the 

 whole we know. 



But yet more important is the probability, nay 

 almost the certainty, that whole formations contain- 

 ing the records of vast geological periods are entirely 

 buried beneath the ocean, and for ever beyond our 

 reach. Most of the gaps in the geological series 

 may thus be filled up, and vast numbers of un- 

 known and unimaginable animals, which might help 

 to elucidate the affinities of the numerous isolated 

 groups which are a perpetual puzzle to the zoologist, 

 may there be buried, till future revolutions may 

 raise them in their turn above the waters, to afford 

 materials for the study of whatever race of intelli- 

 gent beings may then have succeeded us. These con- 

 siderations must lead us to the conclusion, that our 

 knowledge of the whole series of the former inhabi- 

 tants of the earth is necessarily most imperfect and 

 fragmentary, as much so as our knowledge of the 

 present organic world would be, were we forced to 

 make our collections and observations only in spots 

 equally limited in area and in number with those 

 actually laid open for the collection of fossils. Now, 

 the hypothesis of Professor Forbes is essentially one 

 that assumes to a great extent the completeness of 

 our knowledge of the whole series of organic beings 

 which have existed on the earth. This appears to 

 be a fatal objection to it, independently of all other 

 considerations. It may be said that the same ob- 



