INDEX.

Ebert and Ewers emanation from the earth, 508
Electrolysis separation of radio-tellurium by, 25 of solutions of active deposit, 313 of radium solutions, 313 of thorium solutions, 314
Electrometer description of, 90 et seq. use of, in measurements, 90 construction of, 91 et seq. Dolezalek, 94 adjustment and screening of, 95 special key for, 97 application of, to measurements of radio-activity, 97 et seq. measurement of current by, 100 capacity of, 101 use with steady deflection, 103 use with quartz piezo-électrique, 105
Electron definition of, 56 production of, under different conditions, 76 et seq. identity of β rays with electrons, 120 et seq. variation of apparent mass of electron with velocity, 127 et seq. evidence that mass of electron is electromagnetic, 129 et seq. diameter of, 131
Electroscope description of, used by Curie, 85 construction of, for accurate measurements, 86 use of, in measurements of minute currents, 86 of C. T. R. Wilson, 89 use of, in measuring conductivity of air in closed vessels, 531 et seq. use of, for determining radio-activity of ordinary matter, 537

543