3 IS Dr. PiTTON on the Strata below the Chalk. 



groups, forms a range of somewhat lower hills, on the west of that constituted by the superior 

 strata. It is hard enough to be used as a building stone, divides naturally into rhomboids, and 

 contains horizontal seams of argillaceous matter ; but Mr. Rose remarks, that although the hard- 

 ness increases progressively downwards, the increase is not regular nor uniform, some portions 

 as hard as any of the lower occurring in the upper part of it. His list of fossils from the chalk 

 with flints contains about 78 species ; of which, according to Mr. Mantell, only 40 occur in the 

 corresponding part of the formation in Sussex. 



The relations of the lower strata of the chalk are best exhibited in the section at Hunstanton 

 Cliff, which will be presently described. Mr. Rose's list of fossils from the chalk without flints, 

 includes altogether 54 species; of which 30 are found in the upper part of Hunstanton Cliff: — 

 of the whole number only 15 species are wanting in Mr. Mantell's catalogue of the Sussex chalk 

 fossils*. 



Upper green-sand. — It is probable that attentive examination would discover the usual green 

 matter on the confines of the chalk and the representative of the gault in this county : but gene- 

 rally the Upper green-sand is scarcely perceptible. In the section at Mildenhall, inserted above, 

 10 feet of clay mixed with green particles, precede 11 feet of (upper) green-sand with many 

 fossils, which rests on blue clay, no doubt the Gault : and the five feet of sand which occur at 

 the bottom of the boring at Diss may also (possibly) belong to the former. Mr. Murchison 

 considers one of the beds at Hunstanton, as the representative of the malm rock of Western 

 Sussex ; and Mr. Rose also mentions a rock like firestone, on the confines of the chalk, a re- 

 semblance which I find is indicated in my own notes. 



Gault. — This stratum is very distinct at Mildenhall, below green-sand ; and is represented in 

 Smith's map, as occurring all along the line of escarpment, between the lower chalk and the 

 lower ferruginous sand. I have myself seen it with the characteristic fossils at East Winch and 

 several other places. Thus at Mosshill Farm {" Muzzle" of the Ordnance Map), west of the 

 house, towards Denver, are several pits, in a patch, or cap of bluish clay, over the Lower green- 

 sand : the former including Belemnites in great numbers, phosphate of lime in kidney-shaped 

 (coproid) concretions, a few specimens of Ammonites, and fragments of Inocerami in great num- 

 bers. On the heights between Middleton Tower and Devil's Bottom, north of the section, PI. X. a. 

 No. 25, are patches of white and yellowish grey clay, containing many of the Gault fossils ; 

 — Belemnites, Inocerami in fragments. Echinus-spines, and portions of Encrinites. In fact, most 

 of the heights in this part of the country, are thinly covered with gault ; while the sand beneath 

 it rises slowly towards the west. 



The average thickness of the Gault in West Norfolk is not more than 15 feet, according to 

 Mr. Rose, who has traced the connexion between the detached portions, indicated in Smith's 

 map, as far as West Newton, about three miles south of Ingoldsthorpe. The valley between the 

 chalk and Lower green-sand is there interrupted by an advance of the chalk, and beyond that 

 point the blue Gault is no longer observable ; its place being occupied by the red marly stratum 

 of Hunstanton Cliff. The position of this red matter falls in with the strike of the blue Gault in 

 the southern part of the range, at Newton ; and it has been detected, between that place and Hun- 

 stanton, at Dersingham Mill, and at Ingoldsthorpe, where I myself have seen that the red stratum 

 is immediately succeeded by sand, the blue beds being wanting. 



* Geol. Trans. 2nd Series, vol. iii. p. 201, &c. ; and Geology of the South-east of England, 

 (1833.)p. 370, &c. 



