- THE TERTIARY FORMATIONS OF YIRGINIA. 361 



about one and a half miles down the river, at a pretty uniform eleva- 

 tion of fourteen feet A few paces below the Point, the following 

 strata occur. 



1. A layer two feet thick, consisting of a bright yellow mixture of 

 sand and clay, abounding in shells of various kinds, among which are 

 Permi maxilla fa, Oslrea compressirostra, Venus mercenaria, V. cor- 

 tinaria, V. paphia, Isocardia fraterna, Peclen Madisonius, P. Jeffer- 

 sonius, Peclunculus pulvinalus, Corhula inequale and Turritella varia- 

 bilis. 



2. Next a layer six feet thick, composed of mottled ferruginous sand, 

 with a small admixture of clay, containing no shells, but abundant 

 markings, as if shells had once been present in great numbers. 



3. A band of iron sandstone, three inches thick ; and 



4. A dark mould, extending to the top. 



In proceeding down the Potomac, the yellow marl is seen gradually 

 rising higher in the bank. A stratum of blue marl lying beneath it 

 next comes in view, and this continues along the base of the bank, 

 extending some distance out upon the beach, until the shore sinks into 

 a low sandy flat at Ragged Point. 



The Rappahannock cliffs, in Richmond county, nearly opposite to 

 Westmoreland C. H., extend along the river for about four miles, at 

 an average elevation of from forty to sixty feet. Throughout this long 

 range of strata, but little variety is presented. Beds of sandy clay, of 

 various shades of yellow, brown and greenish blue, extend from the 

 water's edge to within a few feet of the top of the bank. In general, 

 the first thirty feet consist of a dark greenish blue mixture of sand 

 and clay, above which is a layer, six feet thick, of similar material, of 

 a brown colour ; next a band of twelve inches of a ferruginous aspect, 

 and over all a stratum of light coloured flaky clay, coated with a yel- 

 lowish and white incrustation of sulphate of lime. Fossils are rare in 

 any of these beds, but multitudes of their casts and impressions maybe 

 found. These embrace a great variety of the smaller shells, some of 

 them of species not frequently met with. Spiculas of gypsum are 

 distributed in the body of the clay, and are particularly numerous upon 

 the surface and in the hollow of the casts, which in general are painted 

 over with the brown oxide of iron. In many places sulphate of iron 



