FUNDAMENTAL RELATIONS OF ANIMALS 103 



study attentively the works of £lie de Beaumont."'' He for the first 

 time attempted to determine the relative age of the different systems 

 of mountains, and showed first also that the physical disturbances 

 occasioned by their upheaval coincided with the successive disappear- 

 ance of entire faunas and the reappearance of new ones. In his earlier 

 papers he recognized seven, then twelve, afterwards fifteen such great 

 convulsions of the globe, and now he has traced more or less fully 

 and conclusively the evidence that the number of these disturbances 

 has been at least sixty, perhaps one hundred. But while the genesis 

 and genealogy of our mountain systems were thus illustrated, palaeon- 

 tologists, extending their comparisons between the fossils of different 

 formations more carefully to all the successive beds of each great era, 

 have observed more and more marked differences between them and 

 satisfied themselves that faimas also have been more frequently reno- 

 vated than was formerly supposed; so that the general results of 

 geology proper and of palaeontology concur in the main to prove 

 that, while the globe has been at repeated intervals and indeed fre- 

 quently, though after immensely long periods, altered and altered 

 again, until it has assumed its present condition, so have also animals 

 and plants living upon its surface been again and again extinguished 

 and replaced by others, imtil those now living were called into ex- 

 istence with man at their head. The investigation is not in every 

 case sufficiently complete to show everywhere a coincidence between 

 this renovation of animals and plants and the great physical revolu- 

 tions which have altered the general aspect of the globe, but it is 

 already extensive enough to exhibit a frequent synchronism and cor- 

 relation, and to warrant the expectation that it will in the end lead 

 to a complete demonstration of their mutual dependence, not as 

 cause and effect, but as steps in the same progressive development of 

 a plan which embraces the physical as well as the organic world. 



In order not to misapprehend the facts and perhaps to fall back 

 upon the idea that these changes may be the cause of the differences 

 observed between the fossils of different periods, it must be well un- 

 derstood that while organized beings exhibit through all geological 

 formations a regular order of succession, the character of which will 

 be more fully illustrated hereafter, this succession has been from 

 time to time violently interrupted by physical disturbances, without 



^^ Notice sur les systemes de montagnes (Paris, 1852). 



