98 FOUR-FOOTED AMERICANS 



'' Of course in climbiiig tins tree we shall only find 

 the living ^Mammals, the extinct species belong to an- 

 other branch of study." 



"What are 'stinct animals ? " asked Dodo. 



"Gone out ones, 1 gness," said Rap, "because 'stin- 

 guishing a candle means putting it out." 



" Make the Avord ea:tinguish and you will be perfectly 

 right, my boy," said the Doctor. 



" I suppose the ones that are dead looked like the 

 live ones, didn't they ? " asked Dodo. 



" By extinct animals the Wise ]\Ien mean not merely 

 those that are dead, but those that lived so long ago 

 that even their exact pattern lias disappeared from the 

 earth, better designs having replaced them." 



" Then how does anybody know about them ? " 

 asked Rap. " By reading in books, I suppose." 



" These animals had passed away before there were 

 any l)ooks, and before man, as we know him, was living 

 on the earth ; so all we can know about them must be 

 learned from the skeletons that are found buried be- 

 neath the earth, and in the rocks and beds of old-time 

 clay and silt. TJie study of these bones is called 

 Pakeontology." 



" How could their bones get into hard rock ? " asked 

 Rap and Xat almost together. 



" That question has a very long answer, and belongs 

 to the story of when the earth was young ; but it will 

 help you to remember this much : — 



" The earth was once a fiery ball of gases like the sun. 

 The time came when it was needed by the Mind that 

 plans and sets everything in motion, and He began to 

 develop it by degrees as He does everything ; for in 



