Mr. Webster on the Strata lying over the Chalk. 227 



admitted of removal from their original situations without being 

 broken. 



These organic remains therefore most distinctly mark the nature 

 of the place where the strata enveloping them have been deposited. 

 It must unquestionably have been the bosom of an extensive lake 

 in some period of the earth far antecedent to human history ; nor 

 can we refrain from emotions of extreme astonishment when this 

 conviction is forced upon us, nor help indulging in speculations 

 on the revolutions which the earth must have undergone, when 

 we consider how very differently these strata are now situated. 

 Instead of being found in a hollow, they now compose the upper 

 part of a hill ; nor are they any more surrounded by those eleva- 

 tions which must have been essential to the confinement of the 

 vast body of fresh water which furnished a habitation to myriads 

 of animated beings, and of which we have nothing to demonstrate 

 the former existence, except the nature of its depositions, which 

 remain a faithful record. 



Over this bed is a stratum of clay 11 feet in thickness, con- 

 taining numerous fragments of a small bivalve shell. The hinge 

 of this shell is of so peculiar a structure that Mr. Parkinson v/as 

 not able to refer it to any known genus. The shells are thin, and 

 unmixed with any other species whatever. It is impossible there- 

 fore to say whether they have belonged to marine or freshwater 

 animals, and I have preferred for the present to keep them among 

 the latter, rather than to suppose another alternation of which 

 there is no direct proof. 



Upon this lies another bed of yellow clay without shells, and 

 then a stratum of friable calcareous sandstone, also without shells. 



To this sandstone succeed other calcareous strata having a few 

 freshwater shells. In these, which, like those mentioned above, 



2 F 2 



