It is mentioned by Woodward that the Woolwich shells are found at Camberwell and Beckenham, on the north-west and south-east sides of the Sydenham Hills. I have other authority for their occurrence at the following places on the south side of the Thames, Camberwell, Redriffe Tunnel, New Cross, Lewisham, Blackheath, Woolwich, Plumsted, Beckenham, Bromley, Chislehurst, Bexley, Cockleshell Bank, two miles south of South Fleet, Windmill Hill near Gravesend, and Higham on the Thames and Medway canal. They are found also at Rungewell Hill near Epsom, and at Headley between Epsom and Dorking.
These localities seem sufficient to warrant us in concluding that the formation of plastic clay extends over a large space in the south portion of the valley of the Thames from Reading to Gravesend.[1]
Woodward mentions oysters as being found on the north side of the Thames in a stratum of sand that covers the chalk near Hertford; this probably is one of the oyster beds of the plastic clay formation.
I remember that in 1806, fire bricks were burnt from some beds of fine sand and clay in the Park at Bulstrode, by the late Duke of Portland, and that moulds for refining sugar were (and are still) made within a mile of it, at some clay pits on the north side of the
- ↑ In Chislehurst, at the north-west angle of the park at Camden Place, the section of a chalk pit displays a great thickness of the ash coloured Woolwich sand, separated from the chalk by the thin pebble bed as at Reading.
The thick Woolwich sand (No. 3,) occurs also at Bexley, where (as is the case in many of the woods about Dartford) shafts 40 or 50 feet in depth have been sunk through it at an early period for the purpose of extracting the subjacent chalk, as is now done at Reading, and Plumsted brick kiln. Mr. Heated, in his History of Kent, conjectures that many of these quarries were excavated by the Saxons, as places of retreat in times of danger. He states that some of them are 20 fathoms in depth, and that they are to be found also near Feversham, and at Fritwood on the south of Marston Passage near Milton. The explanation that is suggested by the geological position of all these places appears to be much more satisfactory.
