Excerpt from Crystallography and Practical Crystal Measurement, Vol. 2 of 2 Consequently, the optical part of a crystallographic investigation is of surpassing interest, and if at times the phenomena prove complicated and require most careful study, the results are not only themselves rendered the more valuable thereby, but the experimental means of arriving at them are intrinsically so beautiful as far more than to compensate for all the trouble involved. 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.

Excerpt from Crystallography and Practical Crystal Measurement The method adopted in this succeeding part of the book has then been to give first a chapter On the symmetry of the crystal system under consideration, and to follow it immediately with another in which a characteristic well-formed crystal of a substance crystallising in that system is actually worked through on the goniometer; indeed in the cases of several of the systems two such crystals of substances belong ing to different classes of the system are thus employed as practical typical examples. In all cases these are chosen either from readily procurable minerals and such as form small well-developed crystals suitable for goniometry, or from easily prepared chemical salts known to afford good crystals without difficulty. From these practical measure ments in each case the symmetry is deduced, the stereographic and clinographic projections of the crystal are accurately drawn, the crystal elements and angles are calculated from the best measured basal angles, and the results are expressed in the approved tabular form, precisely as if for publication. In one of these cases - the measurement of copper sulphate as an example of triclinic symmetry in Chapter XX. - the whole chapter is really a record of an original investigation now published for the first time; for the existing data concerning the crystallography of copper sulphate are so confused that a reinvestigation was imperative. The student is thus enabled to follow an actual piece of research through all its stages. The fact that no two crystals are ever alike entirely saves this method from being a cut-and-dried one, affording no opportunity for original thought and treatment. For the crystals of suitable small size and perfection, purchased from the mineral dealer, or grown in the laboratory by the student personally, with the object of repeating the measurements here detailed and working through the chapter practically with the goniometer, while being similar can never be copies, and will generally afford some additional or different faces, or be deficient in others, compared with those exhibited by the crystal described in this book as typical Of the substance. 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.

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.