Crystallography can be studied from two different view-points: one as a mathematical science with its applications both in the instrumental determination of crystal angles and in their mapping or projection; the other chiefly as an observational study with the application of some simple rules that will enable the student to determine the crystalline form with sufficient accuracy for practical purposes in the field or the laboratory. This book concerns itself with the latter, author presenting his notes in the form of lectures given in the Pennsylvania State College for the use of students. A...