104 F. L. Kitchin and J. Pr ingle — 



Cambridge Greensand of the country towards the north-east. No 

 information on this point could be obtained from published writings^ 

 and an examination of the ground soon showed that the base of the 

 Chalk was not to be seen in any natural exposure. The lower 

 slopes of the escarpment are covered with a deposit of chalky 

 downwash of variable thickness, and the line of outcrop of the basal 

 bed is either concealed beneath this or is situated in the flatter 

 ground under a cover of Boulder-clay. 



The outcrop of the Cambridge Greensand, at the base of the Chalk 

 Marl, is known to extend towards the south-west as far as the 

 neighbourhood of Sharpenhoe, east of Harlington. Here the bed is 

 thinning, and is developed as a bluish-grey sandy clay, about a foot 

 in thickness, with green grains and many nodules. We began our 

 investigations just south of this point, and probed the ground by 

 boring or digging at several localities between here and Wendover. 

 The result was to show that the evidence for a break in the sequence 

 at the base of the Chalk, with signs of erosion, diminishes in a south- 

 westerly direction. 



At a spot one mile south-east of Harlington Church the basement- 

 bed of the Chalk, as shown by fragments brought up by a hand-boring 

 tool, was reached at a depth of 10 feet below the surface. It is over- 

 lain by 3 feet of cream and pale bufi-coloured Chalk Marl, gritty 

 and slightly glauconitic in the lowest foot. The basement-bed is 

 here reduced to a layer which we estimate to be 2 to 3 inches thick. 

 It consists of small well-rounded quartz-grains, black crumbs 

 and polished grains (? phosphate), set in a fine creamy calcareous 

 j)aste containing pebbles (up to | in. in diameter) of rolled quartz- 

 grit, fine quartzose sandstone, and subangular white chert, as well 

 as black phosphatized fragments. This bed is underlain by pale 

 Upper Gault Clay, assuming a darker bluish tint at a lower level. 



At Kateshill, 3 miles north-west of Dunstable, a poor exposure in 

 the road-cutting on Watling Street enabled us to ascertain that the 

 basement-bed of the varians Chalk is an indurated grey calcareous 

 sandstone with numerous small cream and grey-coloured phosphatic 

 nodules, up to \ in. in diameter. This bed is underlain by the pale 

 calcareous clay of the Upper Gault, with darker bluish clay at a 

 lower level, as at Harlington. 



At Totternhoe and Eaton Bray the outcrop of the base of the 

 Chalk is masked by a thick deposit of chalky downwash. It was 

 evidently due to an error that an outcrop of Upper Greensand at 

 the village of Eaton Bray was represented on the Geological Survey 

 majD. The most careful inquiry failed to reveal any trace of it. 

 A boring made in 1913-M at Eaton Bray Nurseries (owned by 

 Messrs. Wallace) on the Chalk outcrop as shown on the map, showed 

 the presence of pale Gault Clay below the Drift. The Lower Green- 

 sand was reached at a depth of 243 feet below the surface. We 

 are indebted to Mr. Wallace, jun., for allowing us to examine samples 

 of the cores in his possession and for communicating to us the details 



