viii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [vol. lxxvi, 



January 21st, 1920. 



Mr. G. W. Lamplugh, F.R.S., President, 

 in the Chair. 



David Buttle, M.I.Mech.E., Iquique (Chile) ; Charles Panzetta 

 Chatwin, University Lecturer in Palaeontology, Geological Depart- 

 ment of the University of Liverpool ; James Davies, 11 Newport 

 Road, Tre Thomas, Bedwas, Cardiff ; Walter Gilbert Langford, 

 M.Sc, Vailala Oilfields (Papua) ; Edward Merrick, M.Sc, 66 Roth- 

 bury Terrace, Newcastle-upon-Tyne; Florence Annie Pitts, Bank- 

 side, Cliftonville, Dorking (Surrey) ; Pierre Pruvost, D.-es-Sc, 

 Maitre de Conferences de Geologie at the University of Lille, 

 159 Rue Brule-Maison, Lille (France) ; Mrs. Eleanor Mary Reid, 

 B.Sc, F.L.S., Pinewood, Milford-on-Sea (Hampshire) ; Howard 

 James Walker, M.I.M.E., Mining Engineer, 8 Park Avenue, 

 Southport (Lancashire) ; and Alfred Kingsley Wells, Assistant 

 Lecturer & Demonstrator in Geology at King's College (University 

 of London), Holmsdale, Buckhurst Hill (Esses), were elected 

 Fellows of the Society. 



The List of Donations to the Library was read. 



Mr. Richard Dixon Oldham, F.R.S., Y.P.G.S., gave a de- 

 monstration on a Model to Illustrate the Hypothesis of a 

 somewhat Rigid Crust resting on a somewhat Yielding- 

 Substratum, as applied to the Problem of the Origin 

 of Mountain-Ranges. 



He remarked that geodetic measurements in the Himalayas, the 

 Pamirs, and the Andes show that in each case there are systematic 

 departures from equilibrium, in the form of parallel zones in which 

 the surface-level stands alternately above and below the level of 

 equilibrium, the differences being very considerable, and amounting 

 to the equivalent of somewhat over 2000 feet thickness of rock of 

 average density. These zones run parallel to the direction of the 

 axis of greatest elevation of the range, and are explicable by an 

 hypothesis that the elevation of the ranges was due to direct uplift 

 produced by changes in volume of the material underlying the 

 crust, if this material be supposed to possess a certain limited 

 amount of compressibility or plasticity and the crust to have a 

 certain amount of rigidity, which would offer resistance to an 

 exact adjustment of the uplift of the surface to the varying amount 

 of uplifting force developed in the material below the crust. 



The model is designed to visualize the consequences of such an 

 hypothesis. It consists of two strips of spring steel, supported at 

 regular intervals by connecting links to a series of blocks capable 

 of vertical movement. For one strip these links are of fixed 

 length, representing a condition in which surface-elevation will be 

 exactly equivalent to the magnitude of the uplifting force. For 



