Royal Institution. 475 



rivers into the sea, which brought down some flints, and arrested the 

 progress of others travelling as beach pebbles along a coast line, 

 in a certain direction determined by the prevailing currents and 

 winds. The spreading of the pebble-bed over a wide area may 

 be accounted for by supposing a gradual subsidence of land, and the 

 continuallyshifting of the coast-lines upon which shingle accumulated. 

 This same subsidence is required to explain the superposition of the 

 London Clay, a deep-sea deposit to the Blackheath or Woolwich beds 

 which are of shallow water or littoral origin. One of the rivers of 

 the Lower Eocene period swept into the sea at Kyson near Wood- 

 bridge in Suffolk the bones of a monkey of the genus Macacus, of a 

 marsupial quadruped allied to the opossum, of a Hyracotherium, 

 and other mammalia, which have been determined by Professor 

 Owen, and which throw light on the inhabitants of the land, at an 

 sera antecedent to the deposition of the London Clay. 



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, 

 attested by these successive assemblages of extinct species, belonging 

 to different tertiary seras, 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 



* Prestwich, Geological Enquiry respecting the Water-bearing Strata 

 around London, &C. Nan Voorst, 1851. 



