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NEW BOOKS
Die Interjerenzen won Rontgen und Elektronenstrahlen. By M. YON LAUE. 22 x 15 cm.; 46 pp. Berlin: Julius Springer, 1935. Price: 3.60 RM. During the autumn of 1935 Professor Laue gave a course of five lectures a t Princeton, N. J., and the admirable suggestion of a wider audience has resulted in the production of this small volume. Laue’s name will always be ass&iated with that of other pioneers in the subject of x-ray interferences, and it is a matter of some interest t h a t his latest work explains not only a newly observed x-ray diffraction effect, but also the elusive phenomenon of the Kikuchi lines in electron diffraction by single crystals. The older theory of x-ray interference, as developed by Laue, Darwin, Ewald, and others, was entirely adequate to explain the positions of the diffraction maxima, but failed in certain little-observed respects with regard to intensities. During 1935 a new phenomenon was observed and reported by Kossel and Voges; the x-rays issuing from a single crystal anticathode act a s a source of radiation within the crystal, and interference effects are observed on a photographic plate placed parallel to the crystal face. The theoretical work of Laue and Kohler joins up the older classical theory with the quantum theory in order to explain these effects, and the bridge between the two is Maxwell’s law of reciprocity. The interesting thing is that the new x-ray patterns are, so far as present results go, entirely similar to the Kikuchi patterns of electron diffraction. Although unexplained details remain, the Kohler-Laue theory work provides a comprehensive theory of these effects. In spite of Professor Laue’s mathematical erudition the reprinted lectures are very readable and deserve translation. J . T. RANDALL. Veroffentlichungen aus dem Kaiser Wilhelm-Institut f u r Silikat Forschung in BerlinDahlem. Siebenter Band. Edited by W. Eitel. 29 x 21 cm.; 203 pp. Braunschweig: F. Vieweg, 1935. The annual reproduction in volume form of the published work of the Kaiser Wilhelm-Institut serves two useful purposes; many of the papers appear in somewhat obscure journals and might otherwise be missed. The volume, apart from the individual merits of the papers, is more useful in indicating the trend of fundamental work on silicates in Germany. The present volume contains twenty-five papers, two of which are concerned with problems of Portland cements; another interesting paper by C. A. Becker contains much information on the physical and chemical properties of complicated glasses containing beryllium oxide. The properties of limesoda-silica glasses containing traces of radium and thorium salts are investigated by &I. Heckter, and this is followed by a long study of the system CaO-SiOa-n;InO with the x-ray identification of solid solutions of pseudo-wollastonite and rhodonite. Biissen gives x-ray data on the coefficients of thermal expansion for magnesia, cristobalite, sillimanite, and carborundum. The volume closes with a very long paper by W. Weyl, giving details of numerous absorption spectra for solutions and glasses. One gets the impression that the workers on this interesting subject are tending increasingly to use physical methods for the study and interpretation of their experiments. J. T. RANDALL. Chemical Discovery and Invention in the Twentieth Century. By SIR WILLIAMA. TILDEN. 492 pp. New York: E. P. Dutton & Co., 1936. Price: $4.00. The sixth edition of this meritorious and semi-popular book has been thoroughly revised by Dr. S. Glasstone of the University of Sheffield. In the preface, Glasstone states that the new material has been selected so as to fit in the structure and con-
