CONTENTS 



CHAPTER VIII. 



POLARIZED LIGHT; THE SIMPLE POLARIZING MICROSCOPE; CRYSTALS UNDER 



THE MICROSCOPE. 



PAGE 



Polarized light, its properties and applications 159 



Isotropic and anisotropic substances 159 



The Nicol prism 160 



Polarizers and analyzers 162 



Testing the adjustments of the polarizing microscope 163 



Centering the rotating stage 164 



Polarized light without a Nicol prism 166 



Fundamental principles of crystallography 167 



Elements of optical crystallography 170 



Directions or axes of vibration of crystals 172 



Use of converging polarized light 173 



Polarization colors 174 



The selenite plate 175 



Absorption of light, pleochroism 176 



Measurement of angles and of extinction angles 177 



Characteristics of the six crystal systems 180 



Experiments with crystals 182 



CHAPTER IX. 



THE DETERMINATION OF REFRACTIVE INDEX BY MEANS OF THE MICROSCOPE. 



The relation between refractive index and contour bands 184 



Principle of the immersion method 185 



Behavior of air bubbles and oil globules 186 



Half-shadow method of illumination 188 



Calculating refractive indices of mixtures of liquids 191 



Refractive index of anisotropic crystals 193 



Uniaxial and biaxial crystals 193 



Determination of the refractive index of liquids 196 



Determination of thickness by refractive index 200 



Liquids for use in the immersion method 201 



Crystals for use in the immersion method 203 



Refractive indices of typical crystals .' 204 



CHAPTER X. 



QUANTITATIVE ANALYSIS BY MEANS OF THE MICROSCOPE. 



Methods available 205 



Analysis of powdered material 206 



Net ruled oculars and their uses . . 208 



