GEOLOGY Chesterford, Hadstock, and Sturmer near Haverhill, includes at its base the Melbourn Rock, named from the Cambridgeshire village of Mel- bourn. This is a hard rocky chalk with marly and nodular layers, about ten feet in thickness. The mass of the Middle Chalk above is well bedded in layers that appear to be lenticular or wedge-shaped, and it has but few flints. Among the fossils are Rhynchonella cuvieri, Terebratulina, and Ho/aster subglobosus. The last-named fossil is found also in a band of hard cream-coloured limestone with green coated nodules and grains of glauconite, known as the Chalk Rock, which separates the Middle from the Upper Chalk. The Chalk Rock has been observed in several places in the northern portions of the county. Between Heydon and Chishall the Chalk is locally disturbed, and instead of the normal southerly or south-easterly dip at a gentle angle, the strata are inclined at an angle of 25 N.N.W., and the flints are fractured. This high dip increases to the south-west in Hertfordshire. Whether the disturbance is due to faulting or to the surface derange- ments produced by glacial agents has not been satisfactorily determined. That glacial action has been potent is manifest from the deeply excavated trough near Newport, to which reference will be made. The Upper Chalk, which lies about 43 feet below the surface near the Thames at Beckton, appears above ground at Grays and Purfleet in south Essex ; and in the north it may be seen at Farnham and Clavering in the Stort valley, at Quendon, Newport, Audley End and Saffron Walden in the Cam valley, and eastwards at Great Yeldham and Middleton, near Sudbury. It consists of soft chalk with layers of flints, and yields remains of the saurian Leiodon (allied to Mosasaurus), of fishes such as Ptycbodus polygyrus, molluscs including Inoceramus and Lima, brachiopods such as Terebratula carnea, the echinoderms Cu/aris and Goniaster, as well as crinoids and corals. At Purfleet, Grays and West Thurrock the Chalk has been largely used in the manufacture of whiting, lime and cement. At Hangman's Wood a remarkable series of excavations known as Deneholes occur. These are shafts carried through about 50 or 60 feet of gravel and Thanet Sand, and 20 feet or more into the Chalk, but as their interest is mainly archaeological they will be described else- where. There is no doubt that the Chalk has been used 'from time im- memorial ' for chalking the land, and more extensively in old days. Arthur Young in 1768, after remarking on the badness of the road between Billericay and Tilbury, observed that ' to add to all the infamous circumstances, which concur to plague a traveller, I must not forget the eternally meeting with chalk-waggons.' He mentioned also that Chalk was brought from Kent by sea to Maldon. 1 At Stifford the Chalk has not only been worked in open pits, but also by means of shafts or ' chalk-wells,' evidence of which was brought 1 A Six Wteki Tour through the Southern Counties, p. 72 ; see also hi General P'ten eftbe Agritulture of Essex, vol. ii. (1807) p. 206. 5
