62 THE STORY OF THE EARTH. 



ogists as the Father of Geology ; and honoured as 

 a great original discoverer in science. 



CHAPTER VIII. 



FOSSILS. 



Geological and Zoological Aspects of Fossil Plants 

 and Animals. 



In the early days of geology fossils were re- 

 garded with interest because some species were 

 limited in their range in time and only found in 

 certain rocks. Attention was given chiefly to 

 extinct species which were most abundant in each 

 of the geological deposits. A large amount of 

 practical work, in mapping the distribution of the 

 strata, was done with the aid of very slight knowl- 

 edge of a few species of animals. 



It became possible also to group the rocks to- 

 gether in a rough way by limitation to the vertical 

 range of a few fossils. The oldest rocks were 

 defined as those containing Trilobites ; the mid- 

 dle group as those containing Ammonites; and 

 the newest group as containing Nummulites. The 



...gist, having to classify the rocks and iden- 

 tify them, was influenced in making divisions of 



the strata occur wherever a difference in life of 



any kind would permit the separation of strata, or 

 groups of strata, from ea< h other. 



A dim idea prevailed that the change in life 



was in some way connected with the succession 



of g( ds Of tune. I [ypothet 



put forward that the groups "1" strata correspond 



