PLASTIC CLAY FORMATION. 257 



subsequently been described by Mr. Webster, and Professor Buck- 

 land*. 



Section of the Strata at Castle Hill, near Newhaven. 



{Beginning with the lowermost deposit.) 



(Vide Tablet vi.) 



Thickness. 



1. Chalk with flints, _ _ _ _ 50 feet. 



2. Ochraceous clay, containing hydrate and suhsulphate of alu- 



niine, and crystallized sulphate of lime, about - - li foot. 



S. Breccia of green sand and chalk flints, the latter covered with 



a green and ferruginous crust, _ _ _ 1 foot. 



4. Sand, of various shades of yeUow, green, and ash colour, 20 feet. 



5. Blue clay with marl of a sulphur yellow colour; including 

 large crystals of sulphate of lime, with fibrous and foliated 

 gypsum, _ _ - - - 20 feet. 



6. A seam of surturbrand, or coal; about - - - 6 inches. 



7. Indurated reddish brown marl, the lower part slaty, contain- 

 ing impressions of leaves, and casts of cerithia, cyclades, &c. a few inches. 



8. Blue clay, containing an immense number of shells, chiefly" 



of the genus cerithium; teeth of a species of squalus, &c. 

 This bed is traversed by a seam of pyrites, a few inches 

 thick, containing casts of cerithia : - - - 



9. Blue clay with broken bivalve sheUs, apparently of the ge- 



nera cytherea, and cyrene, - _ _ _ , 



10. A bed composed almost entirely of oyster shells held together 



by an argillaceous cement, about _ _ _ _ 5 feet. 



11. Diluvium, consisting of yellow and fawn coloured sand, with 



* Residing within a short distance of Castle Hill, the interesting character of its beds 

 had long since engaged my attention; but from want of leisure to arrange the notes I had 

 taken, my observations have been anticipated by the gentlemen above named in every import- 

 ant particular. 



> 10 feet. 



