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NEW BOOKS
Partial Differential; (5) Infinite Series; (6) Partial Differential Equations; (7) Numerical Analysis; (8) Graphical Treatment of Chemical Engineering Processes; (9) Theory of Errors and Precision of Measurements. C. C. FURNAS.
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Ferrorcagnetismus. By R. BECKERA N D W. DORING. 25 x 17 cm.; viii 440 pp. Berlin: J. Springer, 1939. Price: unbound, 39 RM.; bound, 42.60 RM. In the investigation of ferromagnetism there are two groups of questions to be considered: the first is concerned, broadly speaking, with the occurrence of intrinsic spontaneous magnetization, and its magnitude and temperature variation, and the second with the details of the variation with field of the bulk magnetization and with various secondary effects. This book deals mainly with the second group. There are six sections. The first two deal briefly but illuminatingly with fundamental principles and with the general theory of ferromagnetism. The third section, more than a third of the whole book, deals with magnetization processes in ferromagnetics and the factors controlling them. An excellent opening chapter introduces questions connected with crystal, strain, and field energy, describes boundary movement and gradual change of direction of magnetization in spontaneously magnetized regions, and indicates the part they play in the course of magnetization. These topics are discussed in detail in subsequent chapters with reference to initial permeability, coercivity, high frequency permeability, and magnetic after effects. The thermal, electrical, and strain effects accompanying magnetization are then considered, and also the peculiar effects of a magnetic field on elastic properties and on the damping of mechanical oscillations. The final section, which deals with magnetic materials in relation to technological applications, opens with an account of precipitation processes in alloys and their effect on magnetic properties. Technological requirements for different purposes are clearly set forth, and the properties of a large number of both commercial and laboratory alloys are discussed in the light of the general theoretical outlook. From the point of view of a specialist the book is particularly useful for the remarkably comprehensive theoretical treatment, much of which is here published for the first time, of the interrelations between magnetization and strain, both applied and internal. The formal completeness in this one direction does, however, to some extent distort the impression given of ferromagnetism as a whole. None the less, the general parts of the book give good surveys of the present position, and show a wide appreciative knowledge of relevant work, though the selection of references to the literature sometimes seems rather arbitrary. The three hundred and nineteen diagrams, with explanatory captions, are an admirable feature. The table of contents makes the general plan clear, but the index is very inadequate. The book a t once takes its place as a valuable contribution to the literature of magnetism. It will be of great interest, however, not only to magneticians, but also to all those concerned with the properties of metals and alleys. EDMUND C. STONER.
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Reine Metalle. Edited by A. E. VAN ARKEL. 24 x 16 cm.; vii 574 pp. Berlin: Julius Springer, 1939. Price: unbound, 48 RM.; bound, 49.80 RM. The increased interest in the metallic state which has been so conspicuous in recent years has called for a more complete knowledge of the properties of pure metals. Absolute purity being unattainable, and the removal of traces of foreign elements from several of the metals being very difficult, it is important to know what degree of purification has been reached in esch instance, and how products of high
