MODERN GEOLOGY 



those animals which are proper to that fluid medium. 

 If, therefore, we knew the natural history of these 

 solid parts, and could trace the operations of the globe 

 by which they have been formed, we would have some 

 means for computing the time through which those 

 species of animals have continued to live. But how 

 shall we describe a process which nobody has seen per- 

 formed and of which no written history gives any ac- 

 count ? This is only to be investigated, first, in exam- 

 ining the nature of those solid bodies the history of 

 which we want to know ; and, secondly, in examining 

 the natural operations of the globe, in order to see if 

 there now exist such operations as, from the nature 

 of the solid bodies, appear to have been necessary for 

 their formation. 



14 There are few beds of marble or limestone in which 

 may not be found some of those objects which indicate 

 the marine object of the mass. If, for example, in a 

 mass of marble taken from a quarry upon the top of 

 the Alps or Andes there shall be found one cockle-shell 

 or piece of coral, it must be concluded that this bed of 

 stone has been originally formed at the bottom of the 

 sea, as much as another bed which is evidently com- 

 posed almost altogether of cockle-shells and coral. If 

 one bed of limestone is thus found to have been of 

 marine origin, every concomitant bed of the same 

 kind must be also concluded to have been formed in the 

 same manner. 



" In those calcareous strata, which are evidently of 

 marine origin, there are many parts which are of 

 sparry structure that is to say, the original texture of 

 those beds in such places has been dissolved, and a 



