Meteorites of iron coming from other celestial bodies have not shown the presence of radium. Aerolites or stone meteorites have been found to contain as much as similar terrestrial rock. Since the sun contains helium and some stars show its presence as predominating, this suggests the presence of radio-active matter in these bodies. In addition, the spectral lines of uranium, radium, and the radium emanation have been reported as being found in the sun's spectrum and also in the new star, _Nova Geminorum 2_. These observations await further investigation and confirmation. So far as the sun's chromosphere is concerned, the possible amount of radium present would seem to be very small. If this is true, radio-active processes could have little to do with the sun's heat. The statement is made by Rutherford that indirect evidence obtained from the study of the aurora suggests that the sun emits rays similar in type to the alpha and beta rays. Such rays would be absorbed, and the gamma rays likewise, in passing through the earth's atmosphere and so escape ordinary observation. All of this is but further evidence of the unity of matter and of forces in the universe. INDEX Actinium, discovery of, 6 Activity, induced, 17 Alpha particles, effect of loss on Atomic Weight, 45 electrical charge of, 26 form helium, 27 nature of, 25 penetrating power of, 39 position of element changed by its loss, 46 recoil, 39 scattering of, 38 solid, 26 Atom, constitution of, 36 Kelvin's, 37 models of, 37 Rutherford's, 37 Atomic number, determination of, 43 Becquerel's experiments, 2 Beta particles, change in position of element by loss of, 47 Chalcolite, natural and artificial, 4 Constants, table of, 31 Curie unit, 22 Disintegration of the element, 25 Disintegration series, 24 Disintegration theory, 35 Electroscope, 12 Equilibrium series, 22 Helium, characteristics of, 30 discovery of, 29 Ionium, discovery of, 6 Ionization, application of electric field to, 10 experimental confirmation, 9 Ionization of gases, 7 theory of, 8 Ions, size and nature of, 10 Isotopes, 47 Lead, atomic weight varies with source, 45 radio-active, 6 the end product, 45 Life-periods of radio-active bodies, 21 Periodic system, 41 basis of, 42 Polonium, discovery of, 4 Positive nucleus, influence of, 43 Potassium, radio-activity of, 3 Radiations, action on phosphorescent bodies, 13 action on photographic plates, 11 discharge electrified bodies, 12 magnetic deflection of, 14 measurements of, 15 penetrating power of, 13, 15 Radio-active bodies, elemental nature of, 20 examination of, 20 life periods of, 21 Radio-activity, an atomic property, 3 cosmical, 51 influence on chemical theory, 41 products in atmosphere, 51 products in earth's crust, 50 products in soil waters, 50