On the Fossil Shells of the Paris Basin, 207 



in its infancy, is far from an art of minor perfection ; nor is 

 it confined to enquiries merely of more or less exactitude 

 into the chronology of the ages of our earth, but it also 

 attempts to revive, as it were, the forms that peopled the 

 surface of the earth at times anterior to the existence of 

 man, and of which it is impossible to have any other history 

 than the primitive ages have left us in these ancient medals. 

 It is not alone to determine the periods of mineral changes, 

 which are uncertain in their nature, and of comparatively 

 little philosophical importance ; but it is the glory of the 

 geologist, aided by the labours of zoologists and botanists, 

 to collect and arrange materials for the history of each of 

 the great periods during which organic beings were suc- 

 cessively developed, and to bring them by a succession of 

 great events, (sometimes interrupted,) down to the period 

 of authentic history. 



Cuvier in his Recherches sur les Ossemens Fossiles, and 

 M. Brongiart in the example of the great zoologist, have 

 been the first to introduce the study of organic fossils, and 

 Cuvier in particular has afforded, by numerous examples and 

 happy inductions, various beautiful applications of this study 

 to geological pursuits. M. Brongiart afterwards conferred 

 additional value on the study of organic fossils, by extending 

 their application to geological questions, which appeared to 

 him to have remained before without satisfactory solution, 

 and which were capable of illustration by means of those 

 particular organic fossils which formed the peculiar subject 

 of his own study. It is no easy matter indeed to seize for 

 sound geological application, such parts of the science of 

 fossils as are most adapted to the purpose. All branches 

 of the subject are doubtless useful, but all are not so to the 

 same degree ; thus for example, the remains of vertebrated 

 animals are rare, and difficultly determined, diminishing 

 rapidly in proportion as we descend, seldom affording results 

 so general as those of other classes. Thus it must also follow 



