the slightest scientific grounds for assuming that matter existed in a certain condition from all eternity. The essential activity of the powers ascribed to it forbids the thought; for all that we know, and, indeed, as the _conclusion_ from all that we know, primal matter began its progressive changes on the morning of its existence." Finally, in reference to the hypothesis of a unique determination of matter after eternal duration in the past, it may not be out of place to remind the reader of the complexity which modern research ascribes to the structure of the atom. 302 INDEX A. Abney, Sir Wm., on sensitisers, 210. Abundance of life, numerical, 98-100. Adaptation and aggressiveness of the organism, 80. Additive law, the, with reference to alpha rays, 220. Age of Earth, comparison of denudative and radioactive methods of finding, 23-29. Aletsch glacier, 286. Allen, Grant, on colour of Alpine plants, 104. Allen, H. Stanley, on photo-electricity, 203. Alpha rays, nature of, 214; velocity of, 214; effects of, on gases, 214; range of, in air, 215; visualised, 218; ionisation curve of, 216; number of, from one gram of radium, 237; number of ions made by, 237. Alpine flowers, intensity of colour of, 102. Alps, history of, 141; Tertiary denudation of, 148; depth of sedimentary covering of, 148; evidence of high pressures and temperatures in, 149; recent theories of formation of, 150 _et seq._; upheaval of, 147; age of, 147; volcanic phenomena attending elevation of, 147. Andes, trough parallel to, 123; not volcanic in origin, 118. Angle of friction on ice, 261-265, 281-283; on glass, 261-265. Animate systems, dynamic conditions of, 67; and transfer of energy, 71; and old age, 72; mechanical imitation of, 76, 77. Animate and inanimate systems compared, 73-75. Appalachian range, formation of, 120. Arrhenius, on elevation of continents, 17. Aryan Era of India, 136. Asteroids, probable origin of, 175; discovery of, 175; dimensions of, 176; orbits of, 176; Mars' moons derived from, 177. B. Babbage and Herschel, theory of mountain building, 123. Babes (and Cornil), size of spores, 98. Becker, G. F., age of Earth by sodium collection, 14; age of minerals by lead ratio, 20. Berthelot, law of maximum work, 62. Bertrand, Marcel, section of Mont Blanc Massif, 154. Beta rays, nature of, 246; accompanied by gamma rays, 247; production of, by gamma rays, 247; as ionising agents, 249. Biotite, containing haloes, 223; pleochroism of, 235; intensified pleochroism in halo, 235. Body and mind, as manifestations of progressiveness of the organism, 86. Boltwood, age of minerals by lead ratio, 20. Bose, theory of latent image, 203. Bragg and Kleeman, on path of the alpha ray, 215; stopping power, 219; laws affecting ionisation by alpha rays, 220; curve of ionisation and structure of the halo, 232. Brecciendecke, sheet of the, 154. Brdche, sheet of the, 154. Burrard and Hayden on the Himalaya, 138; sections of the Himalaya, 139. C.