48 MIGHTY ANIMALS 



history. So, early the next morning, they were up 

 and about their work. 



Now, the only way it can be known that a rock con- 

 tains a fossil is when a portion of that fossil shows on 

 the surface of the rock. This portion may be so 

 small, and look so much like the rock, that one not 

 experienced in fossil hunting would never see it. 

 But the eye of the man accustomed to this work is so 

 trained that he can detect the slightest indication of 

 a buried bone as soon as he catches sight of it. As 

 countless rocks containing fossils do not show any 

 such indication, and probably never will, the crea- 

 tures which lie buried within them will forever re- 

 main undiscovered. It is very possible that many 

 a picnic lunch has been merrily eaten off a rock in 

 which a skull, or a foot, or some other portion of 

 a gigantic animal is buried, or perhaps the entire 

 skeleton of a smaller creature. Even the founda- 

 tion stones of our homes, or the sidewalks in front 

 of them, may hold the bones of animals unlike any 

 with which we are familiar to-day. 



But there are some sections of the world where the 

 surfaces of many of the rocks have worn away until 



