126 Chronological Arrangement of fossiliferous Deposits. 



With this statement of facts, an excursion into the region 

 of speculation may now be permitted, with the view of testing, 

 more closely than can otherwise be done, the force and truth 

 of that system announced by M. Deshayes, and which pro- 

 fesses to determine the age of deposits by a proportional 

 estimate of their recent and extinct organic contents. I will 

 suppose, then, that one of those indefinite periods of time, with 

 which the mind of the geologist is so familiar, has been com- 

 pleted ; during which the estuary of the Thames shall have 

 been consolidated and elevated, and a section of it exposed 

 to the observation of some future Deshayes, or to a disciple 

 of his school. The investigator proceeds to ascertain the 

 number and proportion of the recent and extinct genera and 

 species, and to assign, upon the strength of this calculation, 

 the rank which the deposit is entitled to assume in the chro- 

 nological scale of nature's works. The sedimentary and 

 tranquil character of the formation, consisting of alternating 

 bands of sand and clay, and the total absence of extraneous 

 materials, give assurance to his conclusions ; and the syn- 

 chronous existence of the organic contents is instanced with 

 unhesitating confidence. He meets with no fact that can 

 excite suspicion, or create distrust: the intrusive and extinct 

 fossils are linked with the recent by the closest of all ties, the 

 attachment by growth of the latter upon the former : they 

 lie in peaceful juxtaposition, and upon undisturbed beds of 

 oysters. But, notwithstanding this concurring and apparently 

 conclusive testimony, it is at once obvious that such conclu- 

 sions and inferences must be directly at variance with truth, 

 and replete with the elements of error. 



The presence of mammalian remains will not avail to 

 disturb the confidence of the enquirer : in his view, they are 

 the representatives of the fauna of the same period to which 

 the formation itself is to be ascribed ; and their presence is to 

 be explained upon the same principles which account for the 

 shallow seas of the present age becoming receptacles for 

 similar remains. 



Thus all is harmonious, but untrue ; all philosophical, but 

 false; and the geologist who looked for safe guidance through 

 the difficulties of his way by means of this talisman ultimately 

 finds himself involved, by its employment, in " confusion 

 worse confounded." 



