CONTENTS. xi 



CHAPTER II. 



LIGHTHOUSES. 



PAGE 



I. Marine Signals The first Catoptric or Reflecting Lighthouses . . 220 

 II. Refracting or Dioptric Lighthouses. Fresnel's Lenses 222 



CHAPTER III. 



THE MICROSCOPE. 



I. The Magnifying Glass, or Simple Microscope 234 



II. The Simple Microscope Wollaston's Doublet 237 



III. The Compound Microscope 239 



CHAPTER IV. 



THE TELESCOPE. 



I. Refracting Telescopes 249 



II. The Inverting Telescope 255 



III. The Erecting Telescope ................ 262 



IV. Reflecting Telescopes 263 



CHAPTER V. 



THE STEREOSCOPE. 



I. Vision in Relief Wheatstone's Reflecting Stereoscope . , , . , , 279 

 II. Brewster's Refracting Stereoscope Helmholtz's Stereoscope Pseudo- 

 scope 283 



' CHAPTER VI. 



PHOTOGRAPHY. 



I. First Attempts at Fixing the Images Produced in the Camera 



Obscura Discoveries of Niepce and Daguerre 289 



II. The Daguerreotype 292 



III. Improvements made in Daguerre's Process 294 



