Mr. Rose's Sketch of the Geology of West Norfolk. 31 B 



and gravel were arranged in the same manner as in those at 

 Litcham. 



Mineral Contents. — Drusy crystals of quartz, with botry- 

 oidal and mammillated chalcedony, both found lining the ca- 

 vities of flints, and pyramidal and rhombic crystals of car- 

 bonate of lime, occupying the interior of shells and echini, are 

 the only minerals we possess : the latter are found in cavities 

 in the chalk in Sussex ; they have not at present been dis- 

 covered in those situations in Norfolk, that I am aware of. 

 Calcareous tufa is deposited by the springs at Swaffham ; the 

 interior of one of the wells was found encrusted to the depth 

 of thirty feet : it commenced about twenty feet from the sur- 

 face, and portions of it were two inches in thickness ; the tex- 

 ture of some of it was porous, other portions were compact, 

 and the surface generally subcrystalline. 



Sulphuret of iron is abundant; it occurs for the most part 

 in spherical balls, having a fibrous structure, radiating from 

 the centre, and terminating on the surface in tetrahedral py- 

 ramids: they frequently inclose a Terebratula as their nucleus. 

 Clusters of columnar crystals of this mineral, as figured by 

 Mantell in * Fossils of the South Downs," tab. 16. fig. 11. 

 are found in the chalk at Swaffham. 



The black oxide of manganese is met with at Castleacre. 

 I found this black power lying in the natural separations of 

 the chalk, about twenty feet from the surface ; it occupies both 

 the oblique and horizontal clefts, but is most abundant in the 

 latter; it is accompanied by and partly mixed with brown 

 oxide of iron and loose chalk. The thickness of this bed at 

 Diss is 330 feet : Hunstanton lies to the west of its escarp- 

 ment, so that it does not extend to the cliff. 



The organic remains are numerous, and the living animals 

 appear to have had favourite localities in the chalk ocean, 

 some individuals abounding in one spot, and not appearing at 

 another : thus, Inoceramus Brongniarti and I. striatus abound 

 at Westacre ; 7. intermedins at Narborough ; L cordiformis at 

 Swaffham ; Pccten Beaveri at Sandringham and Hunstanton, 

 rare at Marham ; Plagiostoma spinosa at Thetford ; P. Hoperi 

 at Swaffham ; Inoceramus involutus at Saham, very rare at 

 Swaffham ; Echinus saxatilis at Litcham ; Cidaris cretosa at 

 Swaffham. Others, inhabitants of the early period of the 

 chalk formation, have vanished in the later period ; among 

 these are the Ammonites of the lower beds, Pecten Beaveri, 

 Spatangus hemisphcericus, Galerites Hawkinsii^Scc. These have 

 been replaced by Ana?ichytes, other Spata?2gi, and large Be- 

 lemnites; the latter are rare, even in the " medial" chalk, for 

 but one has been found at Swaffham. I have also remarked of 



