GENERAL PRINCIPLES. 



259 



Divisions of Geological History. Eras. It is on 



these principles that the whole history of the earth, and 

 the rocks in which it is recorded, has been divided and 

 subdivided. The primary divisions, or eras, are five in 



number, each embodied in a corresponding system of 



rocks : 1. Archasozoic,* in the Archaean or Primary or 



Laureiitiau system of rocks ; 2. Paleozoic, f in the Palaeo- 



* Archaeozoic = primeval animal life, f Paleozoic = old life. 



