CONTENTS

  PAGE
Preface v
CHAPTER    
I. Introduction 1
II. The Masking of Similarity of Symmetry and Constancy of Angle by Difference of Habit, and its Influence on Early Studies of Crystals 10
III. The prescient Work of the Abbé Haüy 22
IV. The Seven Styles of Crystal Architecture 33
V. How Crystals are Described. The Simple Law limiting the Number of possible Forms 50
VI. The Distribution of Crystal Faces in Zones, and the Mode of Constructing a Plan of the Faces 60
VII. The Work of Eilhardt Mitscherlich and his Discovery of Isomorphism 70
VIII. Morphotropy as distinct from Isomorphism 98
IX. The Crystal Space-Lattice and its Molecular Unit Cell. The 230 Point-Systems of Homogeneous Crystal Structure 111
X. Law of Variation of Angles in Isomorphous Series. Relative Dimensions of Unit Cells. Fixity of Atoms in Crystal 121
XI. The Explanation of Polymorphism and the Relation between Enantiomorphism and Optical Activity 133
XII. Effect of the Symmetry of Crystals on the Passage of Light through them. Quartz, Calcite, and Gypsum as Examples 162
XIII. Experiments in Convergent Polarised Light with Quartz, as an Example of Mirror-Image Symmetry and its accompanying Optical Activity 183
XIV. Experiments with Quartz and Gypsum in Parallel Polarised Light. General Conclusions from the Experiments with Quartz 201
XV. How a Crystal Grows from a Solution 236
XVI. Liquid Crystals 255
XVII. The Chemical Significance of Crystallography. The Theory of Pope and Barlow—Conclusion 283
Index 295