ILLUSTRATIONS. 



Lawrence and John Frontispiece. 



The Inverted Image 17 



Illuminated Vapors 25 



Illuminated Spheres 26 



Velocity of Light Astronomical Determination 31 



Velocity of Light Experimental Determination 32 



Reading the Articles 41 



Enlargement as the Squares of the Distances 48 



Practical Results 49 



Degree of Illumination 51 



Comparison of Shadows 55 



Law Verified 55 



Comparison of Lights 56 



Ritchie's Photometer 57 



Ancient Lamp 65 



The Police of old Times 67 



The Ducks on the Lake 78 



Angles of Incidence and Reflection 87 



Mode of Measurement 88 



Apparent Direction 91 



Reflection from Water 94 



The Ghost Illusion on the Stage. 102 



Spectres by a Double Reflection 112 



The Magic Lantern 117 



Ancient Light-house 118 



The Magnesium Lamp 132 



Water from Fire. 137 



Manufacture of Lamp-black 141 



The Bat's Wing 142 



Internal Supply of Air 158 



Electrified Points 165 



Charcoal Points magnified 168 



In a Vacuum ..; 170 



