OBSERVATIONS ON METAMORPHISM. 83 



or re ass of limestone comes directly out of the hypersthene rock near the top of one of 

 the mountains in Essex county, tilled with many of the beautiful minerals I have named 

 above. How, in this case, I would ask any respectable geologist, can the position of this 

 limestone be accounted for on the assumption that it belongs to the Hudson river series? 

 The difficulty, I would remark in anticipation, is not simply apparent, but real ; for the 

 limestone mass does not rest upon, but comes through, the hypersthene rock. This being 

 the fact also in many instances where these minerals abound, I am quite suspicious of a 

 statement that these same identical products are found in an altered blue limestone, in a 

 region too where I know from personal observation that the true primary limestone abounds, 

 and contains the minerals in question. 



Among the characters of a primary limestone, I very early fixed upon the presence of 

 graphite, and believe I was the first who noticed the constancy of this mineral in these 

 peculiar beds. Farther observations have satisfied me of the correctness and value of my 

 earlier ones ; and as yet I have never seen this substance in a stratified limestone of the 

 Taconic series, where, inasmuch as they are the oldest sedimentary limestones, we should 

 expect to find it, if any where. 



Having disposed of the question of metamorphism, as well as of that relating to the 

 origin, age, etc. of the Stockbridge limestone, both of which questions may truly be con- 

 sidered as comprised in one and the same inquiry, I have only to request those who entertain 

 different views, to examine the localities I have referred to in my reports on the New-York 

 rocks, and I have no doubt that the same truths will be enforced on their minds as on 

 my own. I had no theory to support, no preexisting views to maintain. My opinions, 

 therefore, were those which arose out of the circumstances themselves ; they were inductions 

 drawn from facts well considered and well observed. 



§ 7. Brown sandstone or granular quartz. 



Characters and varieties. Occurs in insulated mountain masses. Interlaminations with dark siliceous slates. 

 Opinions in regard to the position this rock holds towards the primary schists. Thickness. Mineral contents. 

 Range and extent. 



This rock is usually homogeneous, finely granular, and crystalline upon a large scale. 

 That it is a sedimentary rock, I have now but little doubt; though its particles are usually 

 fine, the common earthy sedimentary character exists but feebly. 



The common varieties of this rock are, 



1. A coarse breccioid or large pebbly mass at the base. 



2. A fine granular and even-grained rock, of a brown color. 



3. A fine white friable sandstone. 



4. Thin-bedded siliceous slate of a dark color. 



