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chanical designers are less likely t o be acquainted.” Anyone interested in the building of scientific instruments and of precision machines should read this volume. GEORQEGLOCKLER. The Kinetic Theory of Gases. Some Modern Aspects. By MARTINKNUDSEN. Methuen’s Monographs on Physical Subjects. 17 x 11 cm.; 64 ,pp. London: Methuen and Co., Ltd., 1934. Price: 2s. 6d. This book embodies the material of three lectures given in 1933 in the University of London by its distinguished author. It is less a treatise on the kinetic theory than a summary of Professor Knudsen’s own researches, but since these are concerned with several fundamental parts of the kinetic theory, the author has been able to make a connected story of the material. The simpler formulas are deduced, whilst the complicated are merely quoted. The apparatus is described and illustrated. The sections deal with the vapor pressure of mercury, evaporation and condensation, molecular flow through tubes, the cosine law, resistance to motion in gases, thermal molecular pressure, molecular heat conduction and coefficient of accommodation, and the absolute manometer. The treatment is clear and attractive, and the book is one which will be read with interest and profit by many kinds of readers. J. R. PARTINGTON. Gmelins Handbuch der anorganischen Chemie. 8 Auflage. Herausgegeben von der Deutschen Chemischen Gesellschaft. System-Nummer 59: Eisen, Teil A, Lieferung 6. 26 x 18 cm.; xxi 1167-1420 pp. Berlin: Verlag Chemie, 1934. Price: 41.50 Marks. Subscription price: 36 Marks. This volume contains a description of the systems composed of iron and the nonmetallic elements sulfur, selenium, tellurium, boron, and carbon. The treatment is on the lines of the phase rule, although in many cases the chemical properties of the compounds are dealt with in full. The section on the iron-carbon system, in view of its great technical importance, is very detailed, and the volume is essentially a monograph on carbon steels. Nitriding of iron is included. The technical and patent literature is exhaustively covered. The volume is one of exceptional interest and is a valuable summary of a very extensive literature. J. R. PARTINQTON.
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Gmelins Handbuch der anorganischen Chemie. 8 Auflage. Herausgegeben von der Deutschen Chemischen Gesellschaft. System-Nummer 59: Eisen, Teil A, Lieferung 7. 26 x 18 cm.; xxvi 1421-1634 pp. Berlin: Verlag Chemie, 1934. Price: 36 Marks. Subscription price: 31.5 Marks. This volume is concerned solely with the magnetic and electrical properties of iron and steel. The magnetic properties, which are of great technical importance, are very fully described, the section being introduced by a clear account of the general theory of ferromagnetism, including a discussion of the units, the names of which have recently been altered. The text is illustrated by a large number of diagrams and contains much numerical data. The electrical properties include conductivity, thermoelectric properties, contact potentials, discharges between electrodes, and electron emission. The volume is essentially of physical interest and constitutes a valuable monograph on the subjects with which i t deals. The brief accounts of the various phenomena dealt with from the general point of view, and the definitions of the various magnitudes concerned in the effects, will be found very useful for reference by chemists, and the inclusion of x-ray data and lattice constants is a valuable feature. J. R. PARTINQTON.
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