!lLife> 1 



cept in general outline, but broken up into all 

 sorts of shapes that give the varied conditions 

 of landscape that we find whichever way we 

 turn. 



There are but few volcanoes that are active 

 in this age, while in former times they ex- 

 tended for thousands of miles. We still have 

 occasional earthquakes, but undoubtedly they 

 are very slight as compared with those that 

 shook the earth millions of years ago. 



If, now, we study the constitution of the 

 earth's crust so far as it has yet been pene- 

 trated, we find it divided up into periods called 

 Primary, Secondary, and Tertiary. The pri- 

 mary period reaches down to the line where 

 the lowest forms of animal fossils begin to be 

 found. This is called the " Paleozoic " period, 

 which means the period of " ancient life." 

 From here let us first go downward. Im- 

 mediately under this lies a stratum of " Meta- 

 morphic " rocks. To metamorphose is to 

 change; and metamorphic rocks are those 

 which have been changed by heat or pressure 

 from their original formation. This class of 

 rocks lie on top of what are called " Igneous " 

 rocks, which means that they have been 

 formed by or subjected to heat. All lava- 

 formed rocks are igneous. They are unstrati- 

 fied, not in layers or strata, but in a formless 

 mass, and in this they differ from water- 

 formed rocks. 



