Upon examining the shore at low-water, masses of chalk, covered with fuci (sea-weed), &c. are seen protruding through the sands; and towards the base of the cliff a bed of sea-beach is spread upon the sand; a low wall or terrace of white chalk constitutes the boundary of this shingle, as seen in [Lign. 267], c. Thus we perceive, that the present shore is formed by the continuation of the chalk strata of the neighbouring Downs, partially covered with sand and beach, which are the detritus of the flints that have been washed out of previously existing layers of chalk, and ground down by the action of the waves. Now, along the eastern part of the coast, towards Rottingdean and Newhaven, the chalk rises into mural precipices immediately from the sea-shore; but at this place the cliffs are composed of very different materials.[789]
[789] Wond. p. 113; and Quart. Journ. Geol. Soc. vol. vii. pp. 365, 396.
1. In the first place, there is, lying immediately on the terrace of chalk that forms the boundary-wall of the base of the cliff ([Lign. 267], c, and [Lign. 268], c c,), a bed of sand (denoted by the letter o, [Lign. 268]), of irregular thickness and variable extent: from this sand marine shells and the jaw of a Whale (see [p. 778]), have been obtained.
Lign. 268. Cliffs between Kemptown and Rottingdean: seen from the West.
| a.— | Elephant-bed; calcareous strata, containing teeth and bones of Elephants. |
| b.— | Ancient Shingle, or sea-beach. |
| o.— | Red of Sand; containing bones of Whales, and marine shells. |
| c, c.— | Strata of undisturbed Chalk, dipping towards the Downs. |
2. Upon the sand is a bed of loose shingle—a regular sea-beach appearing in no respect different, to the common observer, from that forming at the foot of the cliffs at the present moment; this bed is marked b, in [Lign. 267], and [268]. Upon examining this shingle, it is found to contain numerous pebbles and boulders of granite, porphyry, syenite, and other plutonic rocks (see [p. 34]), none of which occur in the present beach. And in this ancient shingle, teeth and bones of extinct species of Elephant, Horse, and Deer have been discovered. We have here, then, unquestionable evidence that this beach has been formed under conditions altogether different from those which now prevail; for not only is this shingle-bed elevated above the present sea-level, but its contents are of such a nature as could not have been thrown up by the sea, in its present relation to the countries that form its shores.
3. A series of loosely aggregated calcareous deposits, obscurely stratified, rests upon this bed of shingle, and forms the upper portion of the cliff, varying in total thickness from fifty to one hundred and twenty feet. These strata are composed of chalk rubble and loam, with flints partially water-worn, and boulders and pebbles of tertiary sandstone; the whole promiscuously intermingled, and deposited in nearly horizontal layers, from one to three or four feet thick. But the face of the cliff generally presents a weather-worn and crumbling aspect, and large masses are constantly falling down, in consequence of the removal of the ancient shingle, by the effects of the waves at the spring-tides. From the loose state of aggregation of these beds, the fallen masses are speedily washed away, but here and there blocks of great hardness, provincially termed Coombe-rock, remain upon the shore; and, but a few years since, there was a group of high rocks of this kind near the Chain-pier. This compact conglomerate has been produced simply by an infiltration of calcareous spar, which has cemented together the fragments of chalk, flint, &c. In some places, this infiltration has reached the bed of ancient shingle below, and large blocks are occasionally found, consisting of pebbles of flint, granite, &c. held together by veins of calc-spar, in acicular or needle-like crystals. In these sparry conglomerates, the teeth and bones of the mammalia previously noticed are sometimes found.[790]
[790] My daughter discovered part of the lower jaw of a Deer, with teeth, imbedded in this conglomerate, in a mass on the shore near Rottingdean.