548 MESSES. JUEES-BEOWNE AND W. HILL ON THE LOWER PAET 



if Messrs. Reid and Sharman had traced the Chalk-marl through 

 Suffolk and Norfolk, as we have done, and had realized the true 

 position of the hard chalk exposed at Stoke Perry they would never 

 have published their suggestion. 



In our brief communication to the ' Geological Magazine ' we men- 

 tioned that, in order to decide the question, we had a boring made 

 at Stoke Ferry, and had proved the existence of a glauconitic marl 

 there, which rested on blue clay at a depth of 53^ feet below the 

 quarry floor (see p. 556). 



We may also mention in this connexion that from the core of the 

 Glauconitic Marl brought up from the bore at Stoke Perry we ex- 

 tracted a small but perfect cast of Avicula grypJiceoides in dark- 

 brown phosphate of exactly the same appearance as the casts of the 

 same shell in the Cambridge Greensand, so that we feel warranted 

 in regarding this bed as an actual continuation of the Cambridge 

 Greensand. 



Another well-section, at a point a quarter of a mile south-east of 

 the quarry, continues the succession, and shows 58 feet of Gault 

 below the base of the Chalk-marl. The details are as follows : — 



feet. 



Sand and Water 25 



Chalk [t. e. Chalk-marl] 13£ 



Yellow Marl [? Glauconitic bed] 3 



Blue clay [Gault] 56 



Dark green sand 2 



Beds of rock and sand [Lower Greensand] 15 



H4| 



The three feet of " Yellow Marl" we regard as in all probability 

 the glauconitic basement-bed of the Chalk-marl, which has a 

 yellowish tinge, especially when contrasted with the whiter Chalk- 

 marl above, and its assigned thickness agrees very closely with that 

 of the bed proved by our boring. The clay below is, of course, the 

 Gault, and the " dark green sand " is its basement-bed, in which the 

 Coprolites occur at West Dereham. 



For the details of this boring we are indebted to Mr. W. 

 Whitaker, who obtained them from the well-borer himself, Mr. T. 

 Tilley. The three sections taken together, namely, the open quarry, 

 our boring, and Mr. Tilley 's boring, give the complete thickness of 

 the Chalk-marl and Gault at Stoke Ferry, the former being 75 feet 

 and the latter 58 feet in thickness. We had previously calculated 

 the thickness of the Gault, taking the breadth of its outcrop as two 

 miles, and assuming a dip of 1°, to be 59 feet. We shall show in 

 the sequel that the thickness of this clay rapidly decreases from this 

 point northwards. 



On the Gault- area the only sections are those to be seen in liLQ 

 trenches opened from time to time for the purpose of working 

 seam of phosphate-nodules which lies at the base of the clay. T ,, 

 best section open in 1886 was at the works one mile W.N7W. 0 

 Dereham Church ; this showed from 10 to 12 feet of dark grey cla^' 



