380 Reports <& Proceedings — Geologists' Association. 



Geologists' Association. 

 June 4, 1920. 



" The Theory of Isostasy: its geodetic basis and its geological 

 implications." By A. Morley Davies, D.Sc, F.G.S. 



Plumb-line and pendulum anomalies. Historical summary : 

 Bouguer, Petit, Pratt, Airy. 



Static ideas of " compensation " become dynamic in hands of 

 geologists : Osmond Fisher, Button. 



Later geodetic developments : Hayford, Bowie, Burrard. Strength 

 of the earth's crust : Barrell, Oldham. 



Mistaken a^jplications of the principle of isostasy by geologists. 

 Great thickness- of the shallow-water deposits, so far from being a 

 consequence of isostasy, indicate its imperfection. Analysis of the 

 case of the Weald, 



July 2, 1920. 



" On the Beds at the Base of the Ypresian (London Clay) in the 

 Anglo-Franco-Belgian Basin." By L. Dudley Stamp, M.Sc, A.K.C., 

 F.G.S. 



Brief description of typical sections, showing the relation between 

 the London Clay and the Lower London Tertiaries, throughout the 

 London " Basin ". The distinctive fauna of the Blackheath Beds 

 contrasted with that of the underlying Woolwich Beds, and compared 

 with that of the London Clay Basement Bed. Reconstruction of 

 geographical conditions during Lower Eocene times. Evidence 

 of the gradual but intermittent uplift of the Weald and its effect on 

 the deposition of the Eocene beds. 



The succession in Belgium. Description of new and typical 

 sections. Oldhaven Beds. Close relation to deposits of London 

 Area. The succession in the Paris " Basin ". Remarkable similarity 

 of geographical conditions compared with London. The Sinceny 

 Beds — the homotaxial equivalents of the Blackheath (Oldhaven) 

 Beds — have a similar fauna and were found under similar conditions. 



The succession in the Hampshire " Basin ". Connexion with 

 Paris " Basin ". 



Faunal notes on the Blackheath-Sinceny Beds. 



Summary : The London, Belgian, Paris, and Hampshire Eocene 

 regions form parts of one great basin which has a common history. 

 Essential to consider all parts of this basin in any discussion on 

 Eocene rocks of one region. Blackheath-Sinceny IBeds the result 

 of the marine invasion of Ypresian times under special geogi'aphical 

 conditions. Retained as a separate division but part of the Ypresian 

 cycle. Marked change from co2iditions of formation of the under- 

 lying Landenian (Thanet Sands, Woolwich and Reading Beds). 



" On the Stratigraphical and Geographical Distribution of the 

 Sponges of the Inferior Oolite of the West of England." By 

 L. Richardson, F.R.S.E., F.G.S. 



