160 GEOLOGY. 



aiming at the eventual fitness of the earth for man as his 

 habitation. This will be much more obvious to you as 

 we proceed to notice the different ages of the earth's 

 preparation, and show how the continents have grown 

 to be what they are by successive additions. In the 

 case of each continent, the form of the land first lifted 

 above the surface of the waters had a manifest reference 

 to that form which was to be given to it when it was to 

 be completed and made fit for the use of man. There 

 was in the beginning a germ, and the gradual unfolding 

 of it has been beautifully traced out by the labors of the 

 geologist. 



CHAPTER XII. 



RECORD OF LIFE IN THE ROCKS. 



243. Life in the Different Ages of the Earth. There 

 was a period, and that a very long one, as you will see 

 in the next chapter, in which there was no life upon the 

 earth. But after that period was passed, life, vegetable 

 and animal, was introduced, and became, as you have al- 

 ready seen, a great agency in the construction of the 

 earth's crust. What the forms of life were in the succes- 

 sion of ages previous to the age of man have been made 

 out by the geologist, by observing the remains of vege- 

 tables and animals found in the strata of the rocks. The 

 life of the world, then, may be said to have written its 

 own history on tables of stone, and we are able to read 

 on these tables the various changes which the forms and 

 modes of life have taken on during the ages of the past. 

 The lengths of these successive ages we can not make 

 out with any accuracy ; we can not measure time in the 

 far past of our earth by years and centuries as we can 

 in the present age ; but we can, by the life-record, learn 

 the order of succession, which has marked both the con- 

 struction of different parts of the earth and the furnish- 



