Page:Radio-activity.djvu/602

 Wilson, C. T. R. ions as nuclei of condensation, 47 et seq. difference between positive and negative ions as condensation nuclei, 49 equality of charges carried by positive and negative ions, 50 construction of electroscope, 86, 88 natural ionization of air in vessels, 501 radio-activity of rain and snow, 505, 506 loss of charge in closed vessels, 531 et seq., 534 presence of ions in dust-free air shown by condensation, 533 number of ions produced per c.c., 533 effect of pressure and nature of gas on ionization in sealed vessels, 534

Wilson, H. A. charge on ion, 51

Wilson, W. E. radium in sun, 491

Wölfl, Hofmann and Gonder properties of radio-active lead, 27, 413

Wood, A. radio-activity of ordinary materials, 540

Zara, Levi Da and Vincenti radium emanation in spring waters, 516

Zeeman action of magnetic field on light, 77

Zeleny velocity of ions, 42 et seq. difference of velocity of ions, 45 potential gradient between electrodes, 65

Zerban and Hofmann connection of activity of thorium with uranium, 29

Zinc Sulphide scintillations produced in by α rays, 158 cause of luminosity of, 160, 549

CAMBRIDGE: PRINTED BY JOHN CLAY, M.A. AT THE UNIVERSITY PRESS.