It is a bed, however, which is seldom open, and can be worked only at particular tides. It may easily be recognized as lying between the Leaf Bed and the well-marked Lignite Bed, which shows the first traces of salt-water, and where, in the lower portion, _Neritina concava_ may be abundantly found. This last bed may be well seen at Beckton Bunny (Section II.). The lignite, however, though it will give a good deal of heat, will not blaze. Locally it is sometimes used for making black paint. [Illustration: Section II. _of Beckton Cliff immediately to the west of the Bunny_.] Flint gravel—scarcely more than 3 or 4 feet, with an uncertain band of white sand. Lignite—3 inches. Brown clay—3 inches. Lignite—3 inches. Marl and sand—2 feet 2 inches. Ligneous bed, containing shells much broken—8 inches. Grey sand—2 feet 4 inches. Orange-coloured sand, with very few fossils at this point, though plenty eastward—15 feet 9 inches. Olive bed. Fossils abundant—27 feet 3 inches. The present sea-shore. Passing on to Beckton Bunny we reach the first true bed of the Lower Marine Formation, which rises a little eastward of that ravine. I have distinguished it as the Olive Bed, from the abundance of specimens of _Oliva Branderi_, forming the equivalent to number eighteen in Dr. Wright’s arrangement, and which, when worked, emits a strong smell of sulphur. Immediately under the Olive Bed, as seen in the opposite section (II.), taken immediately on the west side of the Bunny, rises grey sand, seventeen feet and a half in thickness, possessing only a few casts of shells. The next bed, however, composed also of grey sand, rising about three hundred yards farther on, is, perhaps, the richest in the whole of this Marine series, and its shells the best preserved. It may at once be recognized by the profusion of _Chama squamosa_, from which it has been called the Chama Bed. Specimens of _Arca Branderi_ and _Solen gracilis_ may be found here as perfect as on the day they were deposited. A little farther on, nearly under the Gangway, rises the Barton clay, encrusted with _Crassatella sulcata_.[272] And here, on looking at the cliff, we may notice how all the beds, as they rise westward, gradually lose their clayey character, and run into sand, which will account for this part of the cliff foundering so fast. The water percolates through the sand down to the Barton Beds, and the loose mass above is thus launched into the sea.