Lewis W.J. A Treatise on Crystallography

Cambridge: At the University Press. – 1899. – 624 p. (Cambridge geological series) My purpose in this text-book is to set before the student the views held at the present time as to the classification of crystals and the principles of symmetry on which the classification is based; to describe the ‘forms’ which are a consequence of the symmetry; to determine the geometrical relations of the forms; and, finally, to explain the methods by which the crystals are drawn and their forms represented graphically. The treatment has been as far as possible geometrical, and, with the exception of the formulae' of plane and spherical trigonometry necessary for the solution of triangles, very little analysis has been introduced into the main discussion. Seeing that good figures are important aids to the understanding of the geometrical relations of crystals, and that practice in drawing crystals develops the student’s power of solving crystallographic problems, I have throughout given prominence to the methods used in making diagrams. The principles of projection followed in the construction of such figures are therefore explained at an early stage. Hence it is necessary in certain parts of Chapters VI and VII to presuppose some knowledge of the crystals of the different systems: and, accordingly, those articles which refer to a given system should be read with the corresponding chapter, and with the examples which it contains. A brief sketch of the methods depending on analytical geometry suitable for the treatment of crystallographic problems has been given in Chapter XIX.Crystals and their formation
The law of constancy of angle
Symmetry
Axial representation
Zone-Indices and Relations of Zones
Crystal-drawings
Linear and stereographic projections
The anharmonic ratio op four tautozonal paces
Conditions for planes and axes of symmetry, and relations Between the Elements of Symmetry
The systems; and some of the physical characters
The anorthic system
The oblique system
The prismatic system
The tetragonal system
The cubic system
The rhombohedral system
The hexagonal system
Twin-crystals and other composite crystals
Analytical methods and divers notations
On goniometers