By Thomas Webster, Member of the Geological Society.
INTRODUCTION.
AMONG the geological researches which have lately been made in various parts of the globe, none have been more interesting than those of M. M. Cuvier and Brongniart in the environs of Paris.
These naturalists have described a series of mineral strata differing in many respects from all that were formerly known, and particularly distinguished by their numerous and singular organic remains. The animals whose exuviæ had hitherto been more commonly noticed in regularly stratified rocks were the inhabitants of an ocean: but many of the Parisian fossils belonged to freshwater lakes and marshes, thus developing new and unsuspected agents in the forming of mineral beds.
The strata described by the French naturalists are deposited in a cavity in the chalk stratum which extends through a considerable part of the north of France. The bottom of this hollow is extremely irregular; and before it was covered by the materials now found in it, must have presented partial cavities and projections, the latter appearing as so many islands piercing through the other strata; and
