THE MECHANICAL PROPERTIES OF WOOD [Illustration: Frontispiece. _Photo by the author_. Photomicrograph of a small block of western hemlock. At the top is the cross section showing to the right the late wood of one season's growth, to the left the early wood of the next season. The other two sections are longitudinal and show the fibrous character of the wood. To the left is the radial section with three rays crossing it. To the right is the tangential section upon which the rays appear as vertical rows of beads. X 35.] THE MECHANICAL PROPERTIES OF WOOD _Including a Discussion of the Factors Affecting the Mechanical Properties, and Methods of Timber Testing_ BY SAMUEL J. RECORD, M.A., M.F. ASSISTANT PROFESSOR OF FOREST PRODUCTS, YALE UNIVERSITY FIRST EDITION FIRST THOUSAND 1914 BY THE SAME AUTHOR Identification of the Economic Woods of the United States. 8vo, vi + 117 pages, 15 figures. Cloth, $1.25 net. TO THE STAFF OF THE FOREST PRODUCTS LABORATORY, AT MADISON, WISCONSIN IN APPRECIATION OF THE MANY OPPORTUNITIES AFFORDED AND COURTESIES EXTENDED THE AUTHOR PREFACE This book was written primarily for students of forestry to whom a knowledge of the technical properties of wood is essential. The mechanics involved is reduced to the simplest terms and without reference to higher mathematics, with which the students rarely are familiar. The intention throughout has been to avoid all unnecessarily technical language and descriptions, thereby making the subject-matter readily available to every one interested in wood. Part I is devoted to a discussion of the mechanical properties of wood--the relation of wood material to stresses and strains. Much of the subject-matter is merely elementary mechanics of materials in general, though written with reference to wood in particular. Numerous tables are included, showing the various strength values of many of the more important American woods. Part II deals with the factors affecting the mechanical properties of wood. This is a subject of interest to all who are concerned in the rational use of wood, and to the forester it also, by retrospection, suggests ways and means of regulating his forest product through control of the conditions of production. Attempt has been made, in the light of all data at hand, to answer many moot questions, such as the effect on the quality of wood of rate of growth, season of cutting, heartwood and sapwood, locality of growth, weight, water content, steaming, and defects. Part III describes methods of timber testing. They are for the most part those followed by the U.S. Forest Service. In schools equipped with the necessary machinery the instructions will serve to direct the tests; in others a study of the text with reference to the illustrations should give an adequate conception of the methods employed in this most important line of research.