FOSSILS, THEIR VAST NUMBER. 



77. These anticipations of Sir R. Murchison have been more 

 than realised by the subsequent researches of M. D'Orbigny, 

 founded upon his own observations, which extended over a large 

 portion of the New as well as of the Old world, and upon the entire 

 mass of facts connected with the analysis of the crust of the earth 

 collected by the observations of the most eminent geologists in all 

 parts of the world. It appears from these researches, that during 

 the long series of periods of geological time from the first appear- 

 ance of organised life upon the globe, to the period in which the 

 human race and the contemporaneous tribes were called into 

 existence, the world was peopled by a series of animal and vege- 

 table kingdoms, which were successively destroyed by violent 

 convulsions of the crust, which produced as many devastating 

 deluges. The remains of each of these ancient creations are de- 

 posited in a series of layers or strata one over the other ; and from 

 an examination of them it has been found that each successive 

 animal kingdom was composed of its own peculiar species which 

 did not appear in any posterior or succeeding creation, but that 

 genera once created were frequently revived in succeeding periods ; 

 that many of these genera, however, became extinct long before 

 the arrival of the human period ; that during the human period no 

 new genus was called into existence, except that of the human 

 race, which, however, according to the idea of the most eminent 

 naturalists, ought to be regarded as an order rather than a genus. 



Each of the succeeding animal kingdoms which thus temporarily 

 inhabited the earth consisted of many hundred species. Thus it 

 has been ascertained byM. D'Orbigny, that there are deposited in 

 the Cambrian or Lower Silurian strata not less than 418 species of 

 the animals which inhabited the globe in the iirst period of its 

 animalisation, and that these included specimens of all the princi- 

 pal divisions of animals from the Vertebrata downwards. 



It will be sufficient, however, for the present, thus briefly to 

 indicate these important discoveries, which we shall develop much 

 more fully in the next volume of these series. 



78. As already explained, the strata, when originally deposited, 

 must in all cases have had a horizontal 



position, and they must succeed each Fig - 25> 



other in their normal order, whenever the fe^fr JL?, 



part of the earth at which they lie has 



undergone no disturbance subsequently 



to the date of their deposition, which has 



sometimes been the case with extensive 



plain countries. In such cases, there- 



fore, a section of the crust would exhibit them in parallel and 



horizontal layers, as in fig. 25. 



71 



