X TABLE OF CONTENTS. 



CHAPTER VII. How THE ELECTRICAL CHARGE ON A 

 CORPUSCLE is ESTIMATED. A NEW 

 USE FOR CLOUDS. 63 



VIII. How THE MASS OF A CORPUSCLE is 

 DETERMINED: DISCOVERY OF THE 

 ONE THING. 65 



IX. PROPERTIES OF CORPUSCLES: CATHODE 



RAYS. 67 



X. POSITIVE IONS: THE OTHER KIND OF 



PARTICLES. 6 



Part 4. Natural Radio-activity : A New Property of Matter. 

 CHAPTER I. ANTECEDENT DISCOVERY. 81 



II. DISCOVERY OF RADIO-ACTIVITY. 86 



III. DISCOVERY OF RADIO-ACTIVE ELE- 



MENTS. 90 



IV. RADIUM. 93 

 V. BECQUEREL RAYS FROM RADIUM. 96 



VI. THE ALPHA-, BETA-, AND GAMMA- RAYS. 105 

 VII. EMANATIONS. 112 



VIII. EMANATION X AND THE BIRTH OF 



HELIUM. 122 



IX. THORIUM, URANIUM, POLONIUM AND 



ACTINIUM. 126 



X. RADIO-ACTIVITY EVERYWHERE. 133 



Part 5. The Resolution of the Atom. 



CHAPTER I. MODERN ALCHEMY: THE TRANSMU- 

 TATION OF MATTER. 137 

 II. ATOMIC DISINTEGRATION: AN AT- 

 TEMPT TO EXPLAIN THE MYSTERY 

 OF MATTER. 150 



III. INTRA-ATOMIC ENERGY. 172 



IV. THE ELECTRICAL NATURE OF MATTER. 179 



