A HISTORY OF HERTFORDSHIRE 



feet, but its limits are not clearly defined in well-borings, and it is almost 

 certain that too great a thickness has been assigned to it there. This 

 may also be the case at Cheshunt. 



From the softness of the Chalk Marl the Lower Chalk at first forms 

 a continuation of the Gault plain, and then a gentle upward slope along 

 the denuded edge of its escarpment up to its junction with the Tottenhoe 

 Stone. This is a hard, rather sandy chalk, from 6 to 1 2 feet thick, and 

 often occurs in two beds, each 3 or 4 feet thick, and separated by a few 

 feet of marly chalk. From its hardness the Totternhoe Stone stands well 

 out above the plain of softer strata, usually forming a distinctive feature 

 in the landscape. It enters the county in the Cam district, at Ruddry 

 Spring near Ashwell, passes through the Ivel district north of Baldock, 

 near Cadwell north of Hitchin, and by Pirton and Hexton. It then 

 enters Bedfordshire, in which county it forms the ridge of Sharpenhoe 

 Knoll, and it has long been extensively worked at Totternhoe as a 

 building-stone, but has not been quarried there for some years. It 

 decays rapidly when exposed to frost and other effects of the weather, as 

 the present state of the west front of Dunstable Priory Church, which 

 is built of it, testifies. It should not be employed for exteriors, but it is 

 admirably adapted for interior decorative work, being at first soft and 

 easily manipulated, and hardening and becoming whiter as the moisture 

 dries out of it. The last which is seen of the Totternhoe Stone in 

 Hertfordshire is in the Thame district north-west of Tring, where it 

 crops out near the summit-level of the Grand Junction Canal south-east 

 of the reservoirs, then forming the ridge of the hill which extends for 

 some distance along the south-eastern side of the Wendover Canal. 



Nearly all along the outcrop of the Totternhoe Stone there are 

 springs at frequent intervals which give origin to deep combes in the 

 north-western escarpment of the Lower Chalk. The water in several 

 instances soon disappears from the surface, being absorbed into the Chalk 

 Marl ; the combes then being formed, or perhaps merely deepened, by 

 underground denudation. The rest of the Lower Chalk consists of about 

 60 to 90 feet of hard grey and white chalk, followed by 4 or 5 feet of 

 grey marly chalk. 



There are two other hard beds in the Chalk of Hertfordshire, the 

 Melbourn Rock and the Chalk Rock. The most recently expressed 

 view is that the former divides the Lower from the Middle Chalk, and 

 the latter the Middle from the Upper Chalk ; but this gives so many 

 divisions to the Chalk that it is best here to consider the Middle Chalk 

 as having the Melbourn Rock at its base and the Chalk Rock at its 

 summit. The Melbourn Rock is a hard, yellow and white, bedded 

 nodular chalk, about 10 feet thick. It may be well seen in a small pit 

 just below Willbury Hill, and it partly surrounds Ravensborough Castle, 

 which is not really a castle but an ancient camp, five miles west of 

 Hitchin. A bed of white chalk, which varies in thickness from about 

 200 to nearly 350 feet, follows. It is more silicious in composition than 

 the Upper Chalk, but has only a few flints irregularly distributed through 



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