In the banks of the Croydon canal at New Cross near Deptford is another section that confirms the place that has been assigned to the Woolwich beds below the London clay, and connected with the plastic. The section does not penetrate so deep as the thick ash coloured sand of Woolwich; but in the canal bank above the bridge we have the following beds laid open, though not sufficiently to ascertain their exact thickness, it does not however vary much from that of the upper beds in the Woolwich pits.
Section at the Canal in New Crors, beginning from the lowest bed.
No.
- Plastic clay abundantly charged with the same shells as in the Woolwich pits.
- Bed of small pebbles chiefly of rolled chalk flints.
- Sandy loam and plastic clay.
- Blue clay full of small selenites, probably the London clay.
The blue clay, No. 4, probably owes its selenites to the decomposition of its shells and iron pyrites; at present no shells are visible near the surface. Its juxta position to the London clay of the Sydenham Hills, of which it seems to be the continuation at their north-east extremity, goes far to identify it with that formation. The plastic clay, No. 3, is used for bricks and coarse pottery in a field adjoining this canal called Counter Hill, close to the New Cross on the east; and the Woolwich shell beds may be seen again at a lock of the canal about a mile above New Cross towards Croydon, in the plain that lies under the east side of the Sydenham Hills. At this lock Mr. Warburton pointed out to me the following shells. Ancilla buccinoides, cerithium denticulatum, cyclas deperdita, a small buccinum, and a small nerite.
