CHAPTER II. 



LITHOLOGY. 



AVING now briefly considered the mineral species that have been 

 found in our state, it is intended in this chapter to describe the 

 rocks that are composed of aggregates of them. Lithology is a geolog- 

 ical science, and therefore it does not deal with small and rare deposits, 

 which, although of interest to the mineralogist, are of little importance 

 in the structure of a world; but whenever a mass of material of such 

 extent as to constitute a feature of the earth's crust is found, this mass 

 is called a rock, and it is considered in the science of lithology. New 

 Hampshire is a favorite field for the pursuit of this study. The surfaces 

 of many states of our country are covered by rocks and soils which pre- 

 sent little diversity; — but we live in a region which has been the scene 

 of disturbances which have uplifted grand mountains and upturned 

 the crust of the earth, presenting to us for our study many most deeply 

 buried strata; and through rifts in these strata the underlying molten 

 matters, which form a very diversified system of eruptive masses, have 

 reached the surface. On our rocks the modifying influences of long 

 ages have left their marks ; and therefore the fundamental question of 

 lithology, — Of what is the earth composed, and how did its constituent 

 rocks reach their present condition ? — becomes one of some complexity, 

 but also one of much interest. 



The age and distribution of our rocks are topics which have been dis- 



VOL. IV. 1 8 



