NATURAL RE VOLITIONS. 



sils are truly the medals of creation, medals which are more Im- 

 portant and incomparably more ancient than all those of Grt.ece 

 and Rome, or the hieroglyphics of Egypt. 



OF THE NATURAL REVOLUTIONS OF THE GLOBE. 



8. The history of the globe, like that of nations, is divided into 

 a certain number of distinct periods, during each of which the 

 state of things changed but little, yet it resembles neither that 

 which preceded nor that which followed after it. 



9. Geologists designate under the term formation, the assem- 

 ble of rocks which were produced during each one of these 

 periods comprised in the interval between two of these revolu- 

 tionary disturbances of the globe. 



10. For example, they give the name of creta'ceous formation 

 (from the Latin, creta, chalk) to the assemblage of rocks which 

 were deposited or derived from the interior of the earth, during a 

 geological epoch, in a part of which chalk was deposited ; and 

 juras'sic formation is the name given to the assemblage of con- 

 temporaneous sedimentary rocks composing the most remarkable 

 strata of the mountains of Jura, &c. 



Beginning with the most ancient, -we will examine these several 

 formations in succession. 



FIRST GEOLOGICAL EPOCH. 

 Primitive, Primary, Primordeal, or Unstratified Rocks.* 



11. Under the name of primitive, or primary rocks (from the 

 Latin, primus, first, before), we ordinarily designate the different 

 rocks which appear to have been formed before the creation of 

 plants and animals, the remains of which are found in less ancient 

 strata, and seem to be a foundation for rocks subsequently pro- 

 duced. 



* Mr. Lyell proposes to designate this system of rocks by the term 

 Hypo'gene (from the Greek, vpo, under, and geinomai, I beget), because 

 they are found under other rocks. He objects to the words primary and 

 primitive, because these terms convey a notion as to the time and age cf 

 the formation, and might lead to the error of supposing that thev were 

 formed before any other rocks were formed, but the term hypo' gene refers 

 exclusively to position. 



8. How is geological history divided ? 



9. What is meant by the term formation ? 



10. What is meant by creta'ceous formation? What is meant by jutnt' 

 *ic formation ? 



1 1. What is meant by primitive, or primary rocks?. 

 23* 



