26 THE UNIVERSE. 



CHAPTER II. 



THE ANTEDILUVIAN INFUSORIA. 



The prodigious abundance of the Infusoria during certain 

 geological periods is one of the most extraordinary facts 

 that the study of nature offers. Although, according to the 

 computations of Ehrenberg, there are sometimes more than 

 a million of these animals in a cubic inch of chalk, yet they 

 swarmed in such numbers, and were so miraculously pro- 

 lific, at the era of this formation, that, in spite of their ex- 

 treme minuteness, some stratified rocks, entirely made up 

 of their calcareous shells, constitute at the present time 

 mountains which take an important place in the mineral 

 crust of the globe. 



Again, microscopists have recently made known a wholly 

 unexpected fact. They have shown that some silicious 

 rocks, known by the name of tripolis, and which to all ap- 

 pearance were homogeneous, are almost exclusively com- 

 posed of the skeletons of several species of Infusoria be- 

 longing to the family of Bacillaria. These skeletons have 

 so faithfully preserved the form of the animals from which 

 they were generated, that men have been enabled to com- 

 pare them with our living species, and recognize that they 

 had the closest analogy with these. 



This remarkable discovery is due to Ehrenberg. He com- 

 municated it to Al. Brongniart on the occasion of a journey 

 the latter made to Berlin. This unexpected revelation so 

 excited the illustrious mineralogist that he wrote the fol- 



