THE 18th Session of the International Geological Congress, originally planned for 1940 and postponed on the outbreak of war, is to be held in Great Britain in 1948, on the invitation of the Geological Society of London. A third circular containing preliminary arrangements for the session has been issued. Meetings will take place in London during August 25-September 1, 1948, and the following subjects have been provisionally listed for discussion : (1) Problems of Geochemistry ; (2) Metasomatic Processes in Metamorphism ; (3) Rhythm in Sedimentation ; (4) Geological Results of Applied Geophysics ; (5) Geology of Iron-Ore Deposits ; (6) Geology of Petroleum ; (7) Geology, Paragenesis and Reserves of the Ores of Lead and Zinc ; (8) Geology of Sea and Ocean Floors ; (9) Pliocene-Pleistocene Boundary ; (10)Faunal and Floral Facies and Zonal Correlation ; (11) Correlation of Continental Vertebrate-bearing Rocks ; (12) Earth Movements and Organic Evolution. Geological excursions covering most of the British Isles, which are planned to take place between August 7 and September 18, form part of the Congress programme. They include sixteen long excursions (7-16 days) before the meetings in London, and sixteen of similar length after the meetings. There will also be daily excursions, centred on London, between August 22 and September 3. Sir Thomas Holland is president of the General Organising Committee and president-designate of the Congress. The general secretaries are Mr. A. J. Butler and Dr. L. Hawkes, and the. treasurer is Mr. F. N. Ashcroft. All communications should be addressed to the General Secretaries, XVIII Session International Geological Congress, Geological Survey and Museum, Exhibition Road, London, S.W.7.