452 



T. V. Holmes — On Deneholes and Bell Pits. 



tributary, would allow, while at Grays the Thames has no tributary 

 stream giving additional access to the land there. As to height 

 above the sea, the three groups are on nearly the same level, those 

 at Bexley being slightly over 100 feet above ordnance datum and 

 that at Hangman's Wood a trifle below. They do not occupy ground 

 of any natural strength, but in each case a slight valley leading up 

 to them would allow fugitives to get to them from the borders of 

 the Thames with but little risk of discovery. 



7. V. J-f. del 



Fig. 3. — Hangman's "Wood, No. 4 Pit. 

 Scale, 40 feet to an inch. Height of chambers, 14 to 16 feet. 



These groups also resemble each other in geological position. In 

 each case the surface bed is either Thanet Sand or gravel overlying 

 Thanet Sand. The greater part of the shaft is in Thanet Sand and 

 ends in the Chalk (see Figs. 2 and 3). Where there is gravel above the 

 Thanet Sand, as at Hangman's Wood, the present mouth of the shaft 

 is much enlarged through the tumbling in of the gravel, while where 

 gravel is absent the Thanet Sand has stood so well that but little 

 enlargement has taken place. The pits at Hangman's Wood are 

 about 80 feet deep, the lowest 22 feet, or thereabouts, being Chalk. 

 Those at Stankey Wood and Cavey Spring average from 20 to 

 30 feet less. The Bexley pits are also smaller in size (judging 



