BOOK REVIEWS.

THE PHILOSOPHY OF PHYSICAL SCIENCE, by Sir Arthur Eddington. 230 pages, 15 X 22 cms. New York, The Macmillan Company, I939. Price $2.50.

The author of this book is well known to a host of readers and thinkers along philosophical lines throughout the world. He is quoted equally as much, if not more than others for his presentations of basic modern thought and opinions, particularly among the lay intelligentsia. There is, therefore, a certain expecta- tion before reading this book, that it leads into worthwhile channels.

The contents of this book represents the substance of the course of lectures delivered by the author as Tamer Lecturer of Trinity College, Cambridge I938. The plan of bringing into view the subject matter gives evidence of careful con- sideration. At the outset it treats with scientific existemology where existemology is defined as that branch of philosophy which treats of the nature of knowledge, and scientific existemology as the sub-branch of existemology which deals with the nature of this part of our knowledge and therefore indirectly with the nature and status of the physical universe to which it formally relates. This gives the tenor of what follows. Examined are the relativity and quantum theories, the concepts of analysis, structure and existence, some very strong and courageous statements on the physical universe, and the development of an outline of a general philosophical outlook which a scientist can accept without inconsistency. To those not directly associated with the broadness of science as here sketched, the book brings a sense of humility and awe of the vastness of the universe, and to those who are more familiar with science generally it brings a recognition to a degree at least of how little is now known and how insecure such knowledge is. The book contains views to which some may not agree but it does set the mind to work and is worthwhile reading.

R. H. OPPERMANN.

DI~.CHARGE }~LECTRIQUE DANS LES GAZ, par Marcel Laporte. 222 pages, illustra- tions, II >( 17 cms. Paris, Armand Colin, 1939. Price 17 ft.

Since the middle of the nineteenth century the phenomena associated with electric discharges in gases have been the subject of numerous investigations, the results of which are of great theoretical and technical importance. To these investigations we owe not only fundamental advances in our knowledge of the constitution of the atom and of the reactions of matter and radiation, but also those applications which, beginning with the utilization of x-rays, are now being extended to the fields of lighting and of electrical engineering, where we may confidently expect some far-reaching developments.

French science, which figured brilliantly at the beginning of this research, has during the last few years kept somewhat aloof, and M. Laporte now fills a lack in the French language on a subject to which he has made a significant personal contribution. He here sets forth, with precision but with a minimum of mathematics, those findings which are most necessary to an understanding of

I35

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