Sodium, deficiency of, in sediments, 44; discharge of rivers, 14. Soils, formation of, 37-39; surface area exposed in, 39. Sollas, W. J., age of Earth by sodium in ocean, 14; thickness of sediments, 6. Spencer, on division of protoplasm, 67. Spores, number of molecules in, 97. Stevenson, Dr. Walter C., and technique of radioactive treatment, 259. Stoletow, photo-electric activity anal absorption, 207. Stopping power of substances with reference to alpha rays, 219. Struggle for existence, dynamic basis of, 80. Strutt, Prof. the Hon. R. J., age of geological periods, 20; radioactivity of zircon, 223. Sub-Apennine series of Italy, 148. Suess, nature of earthquakes. 143. Survival of the fittest and the organic law, 80. T. Talchir boulder-bed, 136. Temperature gradient in Earth's crust, 126. Termier, section of the Pelvoux Massif, 254. Tethys, early extent of, 135-137; geosynclines of, 142. Thermal metamorphism in Alpine rocks, 132, 149. Thomson, James, prediction of melting of ice by pressure, 267. Thorium and uranium, proportionality of, in older rocks, 26. Triple canals, formation of, by attraction of a satellite, 187. Tyndall, colour of ocean water, 55. U. Uniformitarian view of geological history, 15-18. Universe, simultaneity of the, 293-295. Uranium-radium family of elements, table of, 253. V. Val d'Herens, earth pillars of, 33. Van Tillo, nature of continental rock covering, 9. Vegetable and animal systems, relative absorption of energy of, 78. Vegetative organs, struggle between, 105, 106. Volcanoes and mountain ranges, 118; associated with geosynclines, 142; Oligocene and Miocene of Europe, 147. W. Weinschenk and thermal metamorphism, 132, 149. Weismaun, encystment of protoplasm, 68; length of life and somatic cells, 96; origin of death, 83; tendency to early reproductiveness, 98. Wilson, C. T. R., visualised alpha rays, 218. Winchell, progressive changes of matter not eternal, 302. Wood, R. W., on photographic reversal, 211. Z. Zircon, radioactivity of, 223; as nucleus of halo, 223.