It is said that thin strata of a calcareous rock are found in sinking wells through the London clay; but of this I have not seen any well authenticated specimens. The circumstance however is far from being improbable.
The extensive works now carrying on in the neighbourhood of the metropolis, as the cutting the hill at Highgate, the tunnel lately carried under the Thames at Rotherhithe, one under Hyde Park, the canal now forming in the Regent's Park, and several others of a similar kind, have thrown great light upon the nature of the London clay and its fossils, and furnish daily opportunities for observation highly useful to all those who are interested in the examination of our upper strata.
At Highgate-hill the beds consist of
- Vegetable mould.
- Several feet of loose gravel and highly ferruginous masses of sandstone.
- Yellow clay.
- Blue clay, in which great numbers of marine shells and parts of fish were found.
On the south side of the River Thames near Rotherhide, a shaft sunk for a tunnel proposed to be carried under the Thames, exhibited the following strata.
| Feet | ||
| 6 | 9 | Vegetable mould. |
| 9 | 0 | Brown clay. |
| 26 | 8 | Gravel with water. |
| 3 | 0 | Blue clay. |
| 5 | 1 | Loom. |
| 3 | 9 | Blue slay with bivalve shells. |
| 7 | 6 | Gravel stones imbedded in a calcareous rock. |
| 4 | 6 | Light blue soil with pyrites. |
| 1 | 9 | Green sand. |
| 8 | 4 | Leafy clay. |
