The kind of messages referred to. How the electrons have informed man of what the stars are made. How man reads the electrons' wireless messages. How it is other electrons that enable man to read the messages. The real explanation of reflection of light. How light is absorbed by some objects. How some substances are transparent. Why objects appear coloured. What makes the lines in the spectra of stars. The spectroscope 144 CHAPTER XVI HOW MAN PROVED OUR EXISTENCE How man reasoned out a plan for detecting the electron. How the electrons altered some lines in the spectrum. The curious manner in which the Electron informed man that certain stars are approaching this planet, while others are receding from it 158 CHAPTER XVII MY X-RAY EXPERIENCE X-rays are an old story to some electrons. The Electron's personal experience. A very sudden stop. How electrons made a fluorescent screen send out light. The electrons assist the surgeon. A curious find. Detecting imitation diamonds. The Electron and the mummy 166 CHAPTER XVIII OUR RELATIONSHIP TO THE ATOMS How the atoms of matter attract one another. What constitutes the temperature of a body. What the atoms are made of. An important thing still to discover about the atom. The elements. How the electrons produce compound substances. The real explanation of chemical changes 178 CHAPTER XIX HOW WE MADE THE WORLD TALK It was nothing new on the part of the electrons. Exaggerated rumours. The electrons and radium. Fast-flying electrons. Atomic explosions 186 CHAPTER XX CONCLUSION The Electron is made to sum up a few of the wonders which it has related, in order to emphasise the great services which electrons render to man 194 APPENDIX 200 INDEX 211 LIST OF ILLUSTRATIONS PAGE A WELL-KNOWN PHENOMENON PRODUCED BY ELECTRONS _Frontispiece_ DAMAGE DONE BY A PARTY OF ELECTRONS 45 A TOBACCO TIN DEFYING GRAVITATION 79 A MOTOR-CAR WITH WIRELESS TELEGRAPH 99 A TRAIN IMPELLED BY MOVING ELECTRONS 119 PROTECTION AGAINST A DISCHARGE OF ELECTRONS 129 THE SPECTROSCOPE AND THE ELECTRONS' WIRELESS MESSAGES 149 HOW ELECTRONS PRODUCE X-RAY IMAGES 171 CHAPTER I WHAT THE STORY IS ABOUT