Excerpt from Crystallography and Practical Crystal Measurement, Vol. 1 of 2: Form and Structure Besides the new 'chapter concerning X-rays and crystal structure, four other new chapters have been added, largely in response to many requests. In the anxiety not to render the book too large for a single volume, the scope of the first edition was purposely restricted. But the desirability now, after the lessons taught by the War, of giving to English speaking students and investigators, in their own language, both in the British Empire and America, as complete and yet concise an account of the subject as possible, has overborne this consideration, and new chapters have been added on (1) Isomorphism, (2) Polymorphism, Isogonism, and Enantiomorphism, (3) the Thermal Properties of Crystals (additional to dilatation which was already fully, dealt with), and (4) the Electrical and Magnetic Properties of Crystals. The author cannot express his thanks to his critical and Often very helpful reviewers too warmly; besides these new chapters which they recommended it has been found possible to attend to every one of their valid criticisms, to include some account of everything that was specified in the reviews as wanting in the first edition, and to correct every misstatement or slight inaccuracy to which attention was called. Among the more noteworthy additions may be mentioned (1) a very considerable expansion of the chapter on two and three-circle goniometry, and on the use of the gnomonic projection; (2) an illustrated account, for the benefit especially of workers with X-rays, of each of the 65 regular point-systems of Sohncke, and the evolution therefrom of the remaining 165 of the 230 types of possible crystal structure; (3) a considerable enlargement of the chapter on microscopical methods of dealing with small crystals, whether alone or in rock sections; (4) a summary of the magnificent recent work on the structure of the atom, an account of Moseley's law connecting atomic structure with atomic number, which so wonderfully and logically explains the author's own law of progression of the crystal properties in isomorphous series, an epitome of the latest facts concerning radioactivity and the nature of X-rays, and an account of the remarkable revelation of isotopic forms of many of the chemical elements, including the latest discoveries of Dr. F'. W. Aston by means of his positive ray mass spectrograph, all of which are essential to a thorough understanding of the true nature of the perfect solid, a crystal, and of the new avenues of research open to crystallographers. 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.