372 Mr. Rose's Sketch of the Geology of West Norfolk. 



more of the cylindrical form than the nodular; many of them 

 are from eighteen to twenty-four inches in length, and are 

 covered with numerous irregularly formed asperities: these 

 flints are scattered through the chalk like the nodules at other 

 localities. 



At Litcham the layers of flint are placed from four to six 

 feet asunder; their horizontal course is not a plane, but slightly 

 undulating: at the depth of twenty feet a double row occurs, 

 the two layers being about nine inches asunder. 



Our flint is of various shades, from black to gray, and has 

 frequently, in addition to the white coating and lighter zones 

 common to flints, small white circles upon their outer surface, 

 the presence of which I cannot account for. Many flints ex- 

 hibit elegant arborizations on their fractured surface, the stone 

 separating more readily where these vegetations (?) occur; 

 similar dendrites are seen on chalk, and always between the 

 natural divisions of the mineral : these beautiful dendritic con- 

 figurations possess somewhat a metallic lustre upon the black 

 flint when first exposed, and are black upon the gray flint, 

 and soon lose their lustre; they frequently rival the happiest 

 efforts of the artist's pencil. 



The texture of this bed of chalk has an intermediate degree 

 of hardness to that of the lower beds, and those situated to the 

 east at Norwich, belonging to higher strata. Although there 

 is a progressive increase in the compactness of the chalk down- 

 wards, still the hardness varies without any order : blocks, and 

 even fragments of blocks, possessing a hardness not inferior to 

 the lower chalk, are met with in all parts of the bed, but more 

 particularly in the immediate vicinity of the layers of flint; 

 still the chalk in the latter situation is not invariably the 

 hardest. 



The fissures, or " pipes ", occasionally seen in the chalk of 

 Sussex, and also in the " upper " chalk at Norwich*, are 

 rarely observed in the " medial " and lower beds. The largest 

 I have seen in this neighbourhood were in Mr. Lynes's pit at 

 Litcham; they were lined with a brown adhesive clay, and 

 their centre filled with gravel; they are now obliterated. 

 Smaller pipes occur in a pit at Swaflfham, and upon examin- 

 ing the inner surface of the chalk, I found it vertically striated, 

 proving that they were filled from the upper surface : the clay 



from the clay into detached hard stony nodules. The observation of this 

 fact has thrown considerable light on the probable origin of the nodules of 

 flint in chalk, a subject which was very obscure, and of which no satisfac- 

 tory theory had previously been proposed." — Article Iuon, No. 2; in 

 No. 161. of the Penny Magazine, October 4, 1834. 

 * Geology of Norfolk, p. 27. 



