Mountain-building and the geosynclines, 119-121; conditioned by radioactive energy, 125; energy for, due to gravitation, 122; reduction of surface attending, 123; depression attending, 123; instability due to thermal effects of compression, 132; igneous phenomena attending, 132; rhythmic character of, accounted for, 133; movements confined to upper crust, 122; movements due to compressive stresses in crust, 122; movements, rhythmic character of, 121. Mountain ranges built of sedimentary materials, 118. Mueller, J., coefficient of friction of skate on ice, 265, 274. Muth deposits of India, 135. N. Newton, Professor, of Yale, on origin of Mars' satellites, 177. Nucleus, dimensions of, 237; amount of radium in, 238. Nummulitic beds of Himalaya, 138. O. Ocean, amount of rock salt in, 50; cause of black colour of, 55; estimated mass of sediments in, 48; increase of bulk due to solvent denudation, 52; its saltness due to denudation, 41. Old age and death, 82-85; not at variance with progressive activity, 83. Organic systems, origin of, 78. Organic vibrations, 86 _et seq._ Organism and accelerative absorption of energy, 79; and economy, 109-111; and periodic rigour of the environment, 94,95. Organism and sleep, 95; ultimate explanation of rythmic events in, 96, 97; law of action of, 68 _et seq._; periodicity of; and law of progressive activity, 82 _et seq._ P. Penjal traps, 135. Pepys and skating, 273. Perry, coefficient of friction of greased surfaces, 265. Phobos, dimensions of, 177; orbit of, 177. Photoelectric activity and absorption, 207; persists at low temperatures, 208, 209; not affected by solution, 213. Photo-electric experiment, 205; sensitiveness of the hands, 207; theory of latent image, 204, 209 _et seq._ Photographic reversal, experiments on, by Wood, 211; theory of, 210. Piazzi, discovery of first Asteroid, 175. Pickering, W. H., observations on Mars, 167. Planet, slowing of axial rotation of, 189. Plant, expectant attitude of, 109. Pleochroic haloes, measurements of, 224; theory of, 224 _et seq._; true form of, 226; radius of, and the additive law, 225; absence of actinium haloes, 225; see _also_ Haloes; mode of occurrence of, 223 _et seq._ Poole, J. H. J., proportionality of thorium and uranium, 26. Poulton, uniformity of past climate, 17. Pratt, Archdeacon, and isostasy, 53. Prealpes, exotic nature of, 150, 151. Prematerial universe, nature of a, 297, 300. Prestwich and thickness of rigid crust, 128; history of the Pyrenees, 140. Primitive organisms, interference of, 89; life-curves of, 88. Proctor and orbits of Asteroids, 176. Protoplasm, encystment of, 68. Purana Era of India, 134. Pyrenees, history of, 140. R. Radioactive elements concerned in mountain building, 125. Radioactive layer, failure to account for deep-seated temperatures, 127; assumed thickness of, 128; temperature at base of, due to radioactivity, 129; in the upper crust of the Earth, 125; thickness of, 126-128.