326 ON THE DEPOSITS CALLED TERTIARY 



together with vegetable fragments. The whole is 

 followed by the alluvia, which, however interesting 

 from their interred remains, do not concern the pre- 

 sent question. 



In that of the Isle of Wight, the clay is succeeded 

 by various marls, including fresh water shells of dif- 

 ferent species and genera, and, subsequently, by other 

 marls containing mariife shells, followed by strata of 

 calcareous rock, marl, clay, and sandstone, in which 

 the shells belong to fresh water. Thus, here, as in 

 the basin of Paris, it is conceived that there are 

 two deposits from fresh water, separated by one of 

 marine origin. 



I shall leave it to others to apply to these the cri- 

 tical analysis of which I have furnished the grounds : 

 and still more shall I do this as to the London de- 

 posit, on which the remarks ought to be obvious 

 enough. It is one of the cases demanding a decided 

 separation ; as are many more of those formerly enu- 

 merated. To reason from the observations of others, 

 is always sufficiently disagreeable ; when the obser- 

 vations are bad, it is often a hopeless attempt. 

 When such a deposit as that of Oeningen has been 

 called marine, because an obscure shell or doubtful 

 fish was supposed to be such, it is a sufficient ex- 

 ample of the hopelessness of such attempts. At any 

 rate, it is not the business of a systematical work. 



The general conclusion derived from these and the 

 other deposits, as it regards their strata, is now ob- 

 vious. Clay and sand must have been deposited in 

 these circumstances, as it has been in prior states of 

 the globe, and as it is now ; and calcareous matter 

 must have been produced by marine shells ; as, lastly, 

 these strata must have often been indurated into 

 rocks. Sand, clay, marl, sandstone, shale and 



