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

  • Charles Lyell
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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    Sir C. Lyell then exhibited some sections, recently published by Mr. Prestwich,* illustrative of the geology of the environs of London, and gave a rapid sketch of the successive Eocene groups from the London Clay and overlying Bagshot series ■with its nummulites to the Barton and Hampshire freshwater formations with their fossil quadrupeds. He then alluded to the tertiary strata next in the ascending order which he had recently studied in Limburg, Belgium, which are not represented in England, and next to the Miocene faluns of Touraine and the Pliocene strata or crag of Suffolk, and lastly to the still more modern glacial period and the brick-earth of the valley of the Thames. The last mentioned formation contains the bones of extinct quadrupeds mingled with shells of recent species terrestrial and fluviatile. The numerous and important changes in the fauna of the globe, at- tested by these successive assemblages of extinct species, belonging to different tertiary eras, attest the vast lapse of ages, which separate the time when the freshwater beds of Woolwich and Blackheath were formed from the human period. But revolutions of another and no less striking kind have taken place contemporaneously in the physi- cal geography of the northern hemisphere, revolutions on so great a scale that the greater part of the present continents of Europe, Asia, Northern Africa and North America with which the geologist is best acquainted, have come into existence in the interval of time here alluded to. It may also be confidently affirmed that the colos- sal chain of the Alps is more modern than the tertiary shingle of Blackheath. There was deep sea at the period when the London Clay was forming, precisely in the area where the loftiest mountains of Europe now rise into the regions of perpetual snow. In proof of this the Lecturer referred to the works of several modern geolo- gists, especially to those of Sir Roderick Murchison, and to a Lecture delivered by Sir Roderick in the Royal Institution to show that the nummulitic formation which belongs to the Eocene period, and not to the very oldest part of that period, attains an elevation in some por- tions of the Swiss Alps of 8,000 or even 10,000 feet, and enters into the structure and composition even of the central axis of the Alps having been subject to the same movements and partaking of the same foldings and contortions as the underlying cretaceous and oolitic strata. Sir Charles Lyell next proceeded to show that a great series of volcanic eruptions had occurred in Europe since the older Eocene strata of the neighbourhood of London were deposited. Not only Vesuvius and Somma as well as Etna and the extinct volcanoes of Southern Sicily but the trachvtic and basaltic eruptions of the ex- tinct volcanoes of central France are more modern than the London Clay. The evidence consists not only of the superposition of igneous rocks several thousand feet thick, to lacustrine strata of the middle * “ Prestwich, Geological Enquiry respecting the Water-bearing strata around London, &c.” Van Voorst, 1851.
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