370 CONTRIBUTIONS TO THE GEOLOGY OF 



tinning horizontal, while its lower limit approaches the level of the 

 beach. At a point about four hundred yards below the beginning of 

 this layer the strata are as follows : 



1 . Blue clay, one foot in thickness. 



Q. Shelly stratum, seven feet thick, indurated in some places so as 

 to form a rock. This abounds in fossils, among which Carditas are 

 most numerous. 



3. Blue clay, containing copperas, and showing ferruginous stains. 

 Three feet thick. 



4. Clay and sand, in part diluvial. Seventeen feet thick. 



For upwards of half a mile below this the bank presents the same 

 series, the marl occasionallj^, at base, a stratum from four to seven feet 

 thick, consisting of blue clay, sometimes fossiliferous and sometimes 

 without shells, covered by a bed of ferruginous sand and clay, of vary- 

 ing thickness. 



At Boyd's Hole the shelly stratum is not seen, but further down, 

 especially at Albion, and the other localities near Mathias's point, before 

 described, it again makes its appearance in the cliflfs (and furnishes 

 marls of a very useful quality). 



On the Rappahannock, opposite Port Royal, at H. L. Carter's, and 

 other localities on and near this river, the eocene occurs under circum- 

 stances very similar to those which have been described. In the in- 

 terior of the peninsula these strata are revealed in many places at the 

 bottoms of the deep ravines, and in general consist of the dark green- 

 ish blue stratum, containing shells, overlaid by a bed of the gypseous 

 and copperas clays. Frequently, however, only this latter bed is ex- 

 posed in these situations, and some digging becomes necessary to reach 

 the layer containing shells. 



Towards the western limits of the eocene, the shell rock very fre- 

 quently presents itself, and, together with the other strata of the for- 

 mation, generally attains a greater height than in the localities further 

 to the east. 



