236 THE EARTH MADE READY FOR MAN 



caught. So we have their tracks and their bodies all 

 nicely preserved for us in nature's book. 



By the leaves and pictures of this marvelous book 

 we can tell how the earth went on changing and 

 growing; for learned men who love nature have 

 studied the rocks, to read what is told there. They 

 have put together the huge bones there preserved 

 and so can tell us what those strange animals looked 

 like and what kind of feet made those tracks. 



They tell us also that strange birds came which at 

 first looked like winged and feathered lizards, but 

 which changed from age to age until they became the 

 birds we know and love so well. 



There were other creatures of the bird family, 

 something like ostriches. They walked about on 

 the land, being quite too heavy to fly. Queer foot- 

 prints they have left. Men find also the fossil forms 

 of great bats, six times the size of ours, and of enor- 

 mous turtles and crocodiles. Even flies and ants have 

 been preserved from that early time. Only think 

 how much longer ants have been living on the world 

 than human beings. When next you see an ant, stop 

 and think how long its kind has lived upon the earth. 

 Many of the other creatures were too large and too 

 clumsy to adapt themselves to the changing world. 

 So the large creatures died off and gave place to 

 smaller ones. The amphibians, that were once as 

 large as alligators have changed and become in time 

 the frogs and toads that we see; while the reptiles 

 that were so extraordinary in their size and shape 

 have changed also, adapting themselves to the 

 changing world until they have become the turtles, 



