2i8 CLASSICS OF MODERN SCIENCE 

 that the strata happen to be all of them well adapted to preserve the 

 included fossils from decomposition, how many accidents must still 

 concur before these submarine formations will be laid open to our in- 

 vestigation ! The whole deposit must first be raised several thousand 

 feet, in order to bring into view the very foundation ; and during the 

 process of exposure the superior beds must not be entirely swept away 

 by denudation. 



In the first place, the chances are nearly as three to one against the 

 mere emergence of the mass above the waters, because nearly three- 

 fourths of the globe are covered by the ocean. But if it be upheaved 

 and made to constitute part of the dry land, it must also, before it 

 can be available for our instruction, become part of that area already 

 surveyed by geologists. In this small fraction of land already ex- 

 plored, and still very imperfectly known, we are required to find a 

 set of strata deposited under peculiar conditions, and which, having 

 been originally of limited extent, would have been probably much 

 lessened by subsequent denudation. 



Yet it is precisely because we do not encounter at every step the 

 evidence of such gradations from one state of the organic world to 

 another, that so many geologists have embraced the doctrine of great 

 and sudden revolutions in the history of the animate world. Not 

 content with simply availing themselves, for the convenience of classi- 

 fication, of those gaps and chasms which here and there interrupt the 

 continuity of the chronological series, as at present known, they de- 

 duce, from the frequency of these breaks in the chain of records, an 

 irregular mode of succession in the events themselves, both in the 

 organic and inorganic world. But, besides that some links of the 

 chain which once existed are now entirely lost and others concealed 

 from view, we have good reason to suspect that it was never complete 

 originally. It may undoubtedly be said that strata have been always 

 forming somewhere, and therefore at every moment of past time 

 Nature has added a page to her archives ; but, in reference to this 

 subject, it should be remembered that we can never hope to compile 

 a consecutive history by gathering together monuments which were 

 originally detached and scattered over the globe. For, as the species 

 of organic beings contemporaneously inhabiting remote regions are 

 distinct, the fossils of the first of several periods which may be pre- 

 served in any one country, as in America for example, will have no 



