THE TERTIARY FORMATIONS OF YIRGINIA. 353 



Second^ The plantations of Mr Bowen and Dr Welford, in Stafford 

 county, opposite to Fredericksburg, somewhat more than a mile from 

 the town. 



Thinly A locality near, but a little east of Stafford. 



Fourth^ A point on Acquia creek, about one mile below the mouth 

 of Auston's Run. 



Fifth^ A point on the Potomac, between Cook's Landing and the 

 mouth of Meadow Branch. 



An inflected line, passing through these points, will present a close 

 approach to the actual boundary of the eocene, in this portion of the 

 state. 



On the west side of the mouth of Massaponax, the freestone, which 

 constitutes so valuable and interesting a feature in the geology of 

 this district, terminates, and at a short distance below, eocene strata 

 come distinctly into view. Where the main road leading down the 

 Rappahannock crosses the Massaponax, the greenish yellow bed, which 

 frequently forms the highest stratum of the eocene, may be plainly 

 discerned in the hill side, its clayey texture turning off the water, 

 w^iich makes its escape along its upper surface. 



On Snow^ creek, on the edge of Spotsylvania county, and less than 

 a mile to the east of Massaponax, several extensive exposures of the 

 eocene occur. Near the point at which the road before mentioned 

 crosses the creek, a bank of from thirty to forty feet in height exhibits 

 the following series : 



1. A dark bluish green stratum, containing a little sulphateof lime, a 

 considerable proportion of green sand, and a great many shells, among 

 which are eocene Cardita (planicosta?), Cytherea ovata (nobis), Tur- 

 ritella Mortoni. 



2. Stratum of greenish yellow, and somewhat micaceous clay, con- 

 taining some sulphate of lime, and a little sulphate of iron, or copperas. 



3. Stratum of a yellowish brown mixture of clay and sand, with 

 ferruginous markings, indicating the former places of shells. This 

 contains a small amount of sulphate of lime. 



4. An upper bed of diluvial sand and gravel. 



On the same stream, nearer the river, and at the base of the first 

 low grounds, another exposure occurs, which, from the peculiar con- 



