4b ORIGIN OF THE 



CHAPTER III. 



WE have attempted to show some of the geo- 

 logical effects produced upon the earth's surface, 

 by the action of water upon it, during the very 

 gradual reduction of the temperature of its crust. 

 Let us, for the present, confine ourselves to some 

 reflections on the chemical changes wrought 

 upon the surface, by the water and gases sur- 

 rounding the earth, as it passed from an igneous 

 state to that of the temperature we now enjoy. 



We have seen that the gases that now com- 

 pose the air, water, and enter so largely in the 

 composition of vegetable and animal organiza- 

 tion, could not have been a part of the earth 

 while in a molten state ; as we know that a heat 



