Excerpt from Essentials of Crystallography This text is intended for beginners and aims to present the essential features of geometrical crystallography from a standpoint which combines the ideas of symmetry with those of holohedrism, hemih'edrism, etc. All forms possible in the thirty-two classes of symmetry are discussed even though representatives of several of the classes have not as yet been observed among minerals or artificial salts. In each system, however, the important classes are indicated so that the book may readily be used for abridged courses. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.