PROPER SUBJECTS OF GEOLOGICAL INQUIRY. 37 



CHAPTER III. 



Proper Subjects of Geological Inquiry. 



The history of the earth forms a large and complex sub- 

 ject of inquiry, divisible at its outset, into two distinct 

 branches ; the first, comprehending the history of unorga- 

 nized mineral matter, and of the various changes through 

 which it has advanced, from the creation of its component 

 elements to its actual condition ; the second, embracing the 

 past history of the animal and vegetable kingdoms, and the 

 successive modifications which these tw^o great departments 

 of nature have undergone, during the chemical and me- 

 chanical operations that have aflfected the surface of our 

 planet. As the study of both these branches forms the sub- 

 ject of the science of Geology, it is no less important to 

 examine the nature and action of the physical forces, that 

 have affected unorganized mineral bodies, than to investiirate 

 the laws of life, and varied conditions of organization, that 

 prevailed while the crust of our globe was in process of 

 formation. 



Before we enter on the history of fossil animals and vege- 

 tables, we must therefore first briefly review the progressive 

 stages of mineral formations ; and see how^ far we can dis- 

 cover in the chemical constitution, and mechanical arrange- 

 ment of the materials of the earth, proofs of general pros- 

 pective adaptation to the economy of animal and vegetable 

 life. 



As far as our planet is concerned, the first act of creation 

 seems to have consisted in giving origin to the elements of 

 the material world. These inorganic elements appear to 

 have received no subsequent addition to their number, and 



VOL. I. 



