I36 B o o k REVIEWS. [J. F. I.

the various modes of electric discharge in gases and the a t tending luminous phenomena, providing in this small volume from the Collection Armand Colin a guide for s tudents and engineers as well as for the layman who wishes to become acquainted with one of the most active branches of modern physics.

E . E .

THE PHYSICAL EXAMINATION OF METALS, by Bruce Chalmers. Volume I, Optical Methods. 181 pages, illustrations, 15 X 22 cms. NewYork, Long- mann, Green & Co., 1939. Price $4.00.

There are certain methods for the physical examination of metals tha t are perhaps looked upon with uncertainty by many metallurgists, especially those who have had little t raining in physics. While the main properties of light have been put to use in the examination of metals, an understanding of the wave nature of light and associated properties will lead to methods of technique and application toward a more sound knowledge of metals. The author a t tempts in this book to explain some of the physical theory, the more important applications tha t have been made, and to describe technique in some instances. It is volume one of a two volume set, dealing entirely with optical methods. The second vol- ume, yet to appear, will be on other branches of physics as applied to the investi- gation of metals.

A brief account of the properties of light is first given as a foundation for the t rea tment of geometrical optics which goes into the practical almost immediately with examples of the law of reflection in the optical lever. Properties of inter- ference and diffraction are next t reated and some applications touched on here are the measurement of elastic moduli, plane bending apparatus, measurement of size of powders and ultra-violet microscopy. Under polarized light are found investigation of surface changes, relation between optical properties and com- position, and determination of micro-structure, state of strain, presence and nature of inclusions. The concluding chapter of the book examines briefly the process by which light is produced and the relationship to optical methods.

The book is not by any means a complete t rea tment but there is plain evidence of careful selection of channels for most profitable pursuit. A feature is the follow through of the subjects discussed to the point of revealing information on the present known state of results obtained and a frank s ta tement regarding accuracy and dependability. The book is practical and should be of value to metallurgists.

R. H. OPPERMANN.

NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. Report No. 68I, The Unsteady Lift of A Wing of Finite Aspect Ration, by

Robert T. Jones. 8 pages, illustrations, 23 X 29 cms. Washington, Government Print ing Office, 194o. Price IO cents.

Unsteady-llft functions for wings of finite aspect ratio have been calculated by correcting the aerodynamic inertia and the angle of a t tack of the infinite wing. The calculations are based on the operational method.

The s tar t ing lift of the finite wing is found to be only slightly less than tha t of the infinite wing; whereas the final lift may be considerably less. The theory indicates tha t the initial distribution of lift is similar to the final distribution.

Curves showing the variat ion of lift after a sudden unit change in angle of

July, 194o. I BOOK REVIEWS. 137

attack, during penetrat ion of a sharp-edge gust, and during a continuous oscilla- tion are given. Operational equivalents of these functions have been devised to facilitate the calculation of lift under various conditions of motion. As an application of these formulas, the vertical acceleration of a loaded wing caused by penetrat ing a gust has been calculated.

Report No. 682, Flame Speeds and Energy Considerations for Explosions in a Spherical Bomb, by Ernest F. Fiock, Charles F. Marvin, Jr., F rank R. Caldwell, and Carl H. Roeder. 2o pages, illustrations, 23 X 29 cms. Washington, Government Print ing Office, 194o. Price IO cents.

Simultaneous measurements have been made of the speed of flame and the rise in pressure during explosions of mixtures of carbon monoxide, normal heptane, iso-octane, and benzene in a Io-inch spherical bomb with central ignition. From these records, fundamental properties of the explosive mixtures, which are independent of the apparatus, have been computed. The transformation velocity, or speed at which flame advances into and transforms the explosive mixture, increases with both the temperature and the pressure of the unburned gas. The rise in pressure has been correlated with the mass of charge inflamed to show the course of the energy development.

Comparable mixtures of the three hydrocarbon fuels expanded about the same amount upon burning and therefore developed about the same power, despite differences in the rate of burning. The addition of ethyl fluid produced no measurable change in flame speed over the range of conditions studied. None of the characteristics of normal burning seems to give a clue as to the relative tendency of fuels to knock. The observed values of pressure are lower than these calculated on the assumption tha t reaction goes to equilibrium within a very short distance behind the flame front. This fact, together with other independent evidence, points to a continued evolution of energy within gas tha t has already been traversed by flame.

Report No. 686, Stabili ty of Castering Wheels for Aircraft Landing Gears, by Arthur Kantrowitz. 16 pages, illustrations, 23 >( 29 cms. Washing- ton, Government Printing Office, 194o. Price IO cents.

A theoretical study has been made of the shimmy of castering wheels. The theory is based on the discovery of a phenomenon called kinematic shimmy. Experimental checks, use being made of a model having low-pressure tires, are reported and the applicability of the results to full scale is discussed. Theoretical methods of estimating the spindle viscous damping and the spindle solid friction necessary to avoid shimmy are given. A new method of avoiding sh immy- - lateral freedom--is introduced.

LES NOUVELLES M~THODES DU CALCUL DES PROBABILITIES, par Louis Bachelier. 69 pages, 17 X 29 cms. Paris, Gauthier-Villars, 1939. Price 25 fr.

M. Bachelier, since 1927 Professor of the Differential and Integral Calculus at the University of Besancon, is well known for his numerous contributions to the calculus of probability and to the laws of chance. He now gives us a description of his use of certain new concepts which led to a study of questions so complex that our former methods would have been quite inadequate.

138 B o o k REVIEWS. [J. F. I.

Though the discovery of the asymptotic formulae marked the greatest advance ever made in the calculus of probability and though the laws, which are expressed in these and which we owe to De Moivre and to Laplace, comprise what is of real importance in this analysis, yet the knowledge based on these laws and the corresponding theories remained static for almost a century, because the concepts and the means employed permitted the solution of only simple problems. By considering problems calling for new concepts, the author has changed the level of our thinking, adding whole chapters to the calculus of probabilities and bringing simplifications to classical problems.

The asymptotic formulae are, so-to-speak, continuous in space; those which are also continuous in time may be termed hyperasymptotic, the lat ter being exact while the former are approximate. The concept introducing the idea of time assimilates the transformations of probabilities to physical phenomena and gives vital form to a most abstract science. By considering only general theories and by omiting all demonstration and giving merely essential conclusions, the author has been able to condense the hundreds of pages tha t a complete development would require into the small compass of this work.

E . E .

SEMI-CONDUCTORS AND METALS, by A. H. Wilson. I19 pages, illustrations, tables, 15 X 22 cms. New York, The Macmillan Company, 1939. Price $2.oo.

From time to time in these pages mention is made of accounts on various subjects known as the Cambridge Physical Tracts. This book is one of this series of accounts with the aim of simplifying some of the main achievements of the theory of metals in the last ten years.

I t begins with a t rea tment of fundamental ideas which are necessary for a rough quali tat ive survey of the subject and proceeds into the energy levels of a three dimensional crystal giving general theory required for discussions of the finer details. The remaining chapters are devoted to the applications of the results. They cover specifically the structure of metals, semi-conductors, the thermal and magnetic properties of metals and conductivity.

The author realized the difficulty of t reat ing so complex a subject in a sim- plified manner and to supplement this work a list of references is given for fuller understanding. Those who are familiar with the status of the subject will find this work valuable.

R. H. OPPERMANN,

A SHORT HISTORY OF SCIENCE, by W. T. Sedgwick and H. W. Tyler. Revised by H. W. Tyler and R. P. Bigelow. 512 pages, plates, illustrations, 15 X 22 cms. New York, The Macmillan Company, 1939. Price $3.75-

A knowledge of the history of science is of as great a value to the layman today as knowledge of political and economic history, for science plays a part of equal importance and is destined to at least continue in this position. For men engaged in scientific pursuits or in the application of science, a background of history is necessary to gain greater appreciation of the subject. Therefore, when a book on the subject makes its appearance, curiosity is aroused with regard to the ex- tent of its coverage as well as its method of presentation.