ARTICLE XIII. 



Contributions to the Geology of the Tertiary formations of Virginia. 

 — Second Series. By William B. Rogers^ Professor of Natural 

 Philosophy in the University of Virginia, and Henry D. Rogers, 

 Professor of Geology and Mineralogy in the University of Penn- 

 sylvania, Read March 1, 1839. 



GEOLOGY OF THE PENINSULA BETWEEN THE POTOMAC AND RAPPA- 

 HANNOCK RIVERS. 



The portion of the state referred to under this head, embraces the 

 counties of Lancaster, Northumberland, Richmond, Westmoreland 

 and King George, together with the eastern part of Stafford county, 

 thus including the district usually denominated the Northern Neck, 

 and extending some distance beyond it to the west. 



This area forms the northern portion of the tertiary region of Vir- 

 ginia, presenting extensive deposits of each of the two subordinate di- 

 visions of the tertiary formation, which were described in our former 

 paper as occupying the tidewater districts of the state. The more 

 recent of these subordinate formations, the meiocene, or middle tertiary, 

 extends from near the bay shore, westward, over the larger portion of 

 the peninsula ; while the older, or eocene deposit, occupies the remain- 

 ing area on the west. The precise boundaries of these formations, as 

 recently determined, will be hereafter described. 



VI. — 4 M 



