286 BOOK REVIEWS. [J. F. 1.

that these might be best left to the suggestion of the teacher. There is a very large amount of valuable information contained in the book.

HENRY LEFFMANN.

HANDBUCH DER EXPERIMENTALPHYSIK. Band I3, 2. Tell. Physik der Gltihelek- troden, by Prof. Dr. W. Schottky and Dr. Ing. H. Rothe, 55 illustrations; Herstellung der Gltihelektroden, by Dr. Rer. Techn. H. Simon, 36 illus- trations; Technische Elektronenr6hren und ihre Verwendung, by Dr. Ing. H. Rothe, 88 illustrations. 492 pages. Edited by W. Wien and F. Harms with the collaboration of H. Lenz. Leipzig, Akademische Verlagsgesell- schaft M. B.H. 1928.

This volume which is one of the series comprising the "Handbuch der Experimentalphysik" (Handbook of Experimental Physics) is typical of the extensive and thorough treatment accorded the subjects of its contemporary volumes. The subject matter has been divided into three parts. Part one, The Physics of Incandescent Electrodes is presented in an able and comprehensive manner by W. Schottky and H. Rothe. The authors have sought to treat the problem of the emission of electrically charged particles from hot bodies in the light of thermodynamical considerations rather than statistical. The term. "#-thermodynamics" is employed to designate the application of the regular thermodynamic equations to the characteristics of individual electrified particles, Particular attention is paid to the correlation between theoretically calculated values and those obtained experimentally. In this connection the investigation of thermionic emissions by Langmuir and associates received particular attention.

Part two, on the "Preparation of Incandescent Electrodes," written by H. Simon, has a preliminary study upon the characteristic emissions of polished metals, metals coated with other metals possessing a high emissivity and metals having a coating of metallic oxide. Methods for producing a high vacuum, measuring the same, determining temperature and preparing a glowing cathode tube are treated all with considerable detail.

Part three, by H. Rothe, on Technical Electronic Tubes and their Appli- cations, embraces a discussion upon the present day widespread use of vacuum tubes as amplifiers, oscillators and detectors. Characteristic curves and equa- tions are given indicating the performance of various types of tubes and their seemingly infinite variety of hookups.

The book is an excellent treatise and a general work of reference upon the subjects in question and the authors are to be commended for their compilation and critical treatment of the subject matter presented therein.

T. K. CLEVELAND.

VIBRATION PROBLEMS IN ENGINEERING. By S. Timoshenko, Professor of Engineering Mechanics, University of Michigan. vi-351 pages, illustrations, 8vo, cloth. New York, D. Van Nostrand Company, Inc., I928. Price,

$4.50. Among the numerous specialties of modern engineering practice, the study of

the vibration of machines and of structures which carry moving loads, and problems of kindred nature may justly claim to have achieved a position of

Feb., 1929.] BOOK REVIEWS. 287

recognized importance. In the past, vibrat ions of machines, and their more or less injurious and sometimes decidedly unpleasant effects upon the immediate surroundings were more often endured ~han cured. Now, they are more often cured or prevented by the application of century-old principles which have only needed the quickening touch of modern vision. A member of this Insti tute, Mr. N. W. Akimoff, one of the init iators of the modern practice of vibrat ion engineer- ing, during the trying months of our entry into the Great War, by the application of these principles, it is related, won the distinction of put t ing into service a nluch- needed naval vessel which had proved quite useless for its intended purpose on account of destructive vibrat ion at high speeds.

Professor Timoshenko develops fully the theory of vibrations, its formulation and its application to the solution of technical problems. This he illustrates by various examples, in many cases, taken from actual experience with vibrat ion of machines and machines in service. The subject-matter is based upon a series of lectures on vibrat ion which he delivered before the mechanical engineers of the Westinghouse Electric and Manufactur ing Company during the year 1925 . The t rea tment is rational and deductive in first dealing with general equation of motion and then passing to specific cases. The list of topics is long and repre- sentative, and their t rea tment thorough and practical.

LUCIEN E. PICOLET.

ENZYME ACTIONS AND PROPERTIES. By Ernst Waldschmidt-Leitz, Ins t i tu t ffir Biochemie, Deutsche Technische Hochschule, Prag., formerly at the Uni- versity of Munich. Translated and extended by Robert P. Walton, Depart- ment of Organic Chemistry, Colmnbia University. 255 pages, illustrations, 8vo. New York, John Wiley & Sons, Inc., 1929. Price, $4-

The nature and mode of action of enzyms are among the most interesting and difficult problems of organic chemistry. The subject is especially associated with bio-chemistry, since a large group of enzyms are produced only in living tissues. The present work is limited to this group, bu t the enzymist must not overlook the part played by inorganic bodies in actions essentially similar in result to those produced by those of organized origin. Broadly speaking, all substances tha t affect the speed or products of a reaction without being themselves changed may be classified as catalysts, and there is no necessity for culling out the organic phenomena and designating them by a special name. It is the province of science to connect objects and phenomena tha t are analogous as well as to distinguish them when the analogy is only apparent .

The present work is a translat ion from German with considerable additions. The original is not available to the reviewer, and no judgment can be made as to the general accuracy of the translat ion nor as to the extent of the additions, but as the t ranslator has been closely associated with the author ~ . l ~ s had the lat ter 's direct assistance during the preparation of the book, it i~evident}that the original is correctly represented. In the course of reading, a sing~"[hadvertence has been noted, the adjectives " fo rmed" and " u n f o r m e d " are used to designate the old distinctions between "organ ized" and "unorgan ized" ferments, and the former terms are given as the accepted English terms, but they were not so used.

The work covers a wide field within the specific limits assigned to it, tha t is, the enzyms producing changes in organic substances. Modern research, part ly