CHAPTER II. 
LITHOLOGY. 
woe 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. 18 
