Plate (Fig. 33) 
TABLE OF CONTENTS. 
Radio-active Substances . 
Ionization Theory of Gases 
Methods of Measurement 
Nature of the Radiations 
Rate of Emission of Energy . 
Properties of the Radiations . 
Continuous Production of Radio-active Matter 
Radio-active Emanations 
Excited Radio-activity 
Radio-active Processes 
Radio-activity of the Atmosphere and of Ordinary Materials 
Index 
to face p. 169 
