On the Blackheath pebble-bed, and on certain phaenomena in the geology of the neighbourhood of London / Sir Charles Lyell.

  • Lyell, Charles, Sir, 1797-1875.
Date:
[1852]
Catalogue details

Licence: Public Domain Mark

Credit: On the Blackheath pebble-bed, and on certain phaenomena in the geology of the neighbourhood of London / Sir Charles Lyell. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    upwards, and draw in water to lubricate its gills, and reject it when it has served the purposes of respiration. The water at Mobile is usually fresh, but sometimes brackish. Sir Charles examined lately the Woolwich beds with Mr. Morris, and they verified Mr. De la Condamine’s observations, observing there several dozen specimens of the Cyrena tellinella in an erect position. From this circumstance the Lecturer infers, that a body of fresh or river water had been maintained permanently on that spot during the Eocene period, and the presence of rolled oysters in the associated pebbly layers, with other marine shells, mixed with species of Melanopsis, Melania, Cerithium and Neritina demonstrate that the sea occasionally invaded the same area. To an overflow of the pebbly sand in which the Cvrense lived by salt water, may probably be attributed the poisoning of the mollusks which left their shells uninjured on the spot where they had lived. The stratum called “ the shell-bed,” which contains at Greenwich, Woolwich, Upnor near Rochester, and other places, a great mass of fresh water, brackish-water and marine shells, especially oysters, is observed everywhere to underlie the great pebble-bed. Its mode of occurrence implies the entrance of one or more rivers into the Eocene sea in this region. Other rivers draining adjoining lands are indicated by a similar assemblage of fluvio-marine fossils near Guildford and at Newhaven in Sussex. The vicinity of land to the South and West of Woolwich is shown by the occurrence at New Cross, Camberwell, and Chelsea of Paludina and Unio in strata evidently a prolongation of the Woolwich beds, and by fossil leaves of dicotyledonous trees and layers of lignite in some of those loca- lities. On the other hand at the junction of the “ London Clay,” and the subjacent “ plastic clays and sands,” when followed in an opposite or easterly direction towards Herne Bay and the Reculvers, ill signs of the freshwater formation disappear, and the pebble-bed is reduced to a thin layer, often a foot or a few inches in thickness. The origin of this shingle may have been chiefly due to the action of waves on a sea-beach. Its accumulation in great force at certain ooints where freshwater shells abound, seems to imply the entrance of •ivers into the sea, which brought down some flints, and arrested the progress of others travelling as beach pebbles along a coast line, n a certain direction determined by the prevailing currents and vinds. The spreading of the pebble-bed over a wide area may >e accounted for by supposing a gradual subsidence of land, and the :ontinually shifting of the coast-lines upon which shingle accumulated, ’his same subsidence is required to explain the superposition of the London Clay, a deep-sea deposit to the Blackheath or Woolwich beds rhich are of shallow water or littoral origin. One of the rivers of he Lower Eocene period swept into the sea at Kyson near Wood- ridge in Suffolk the bones of a monkey of the genus Macacus, of a aarsupial quadruped allied to the opossum, of a Hyracotherium, ■ jnd other mammalia, which have been determined by Professor Owen, nd which throw light on the inhabitants of the land, at an era an- acedent to the deposition of the London Clay.