ubject. More than eighty thousand tests
have been made at the Madison laboratory alone, and the work is
far from completion.

The writer also acknowledges his indebtedness to Mr. Emanuel
Fritz, M.E., M.F., for many helpful suggestions in the
preparation of Part I; and especially to Mr. Harry Donald
Tiemann, M.E., M.F., engineer in charge of Timber Physics at the
Government Forest Products Laboratory, Madison, Wisconsin, for
careful revision of the entire manuscript.

SAMUEL J. RECORD.
YALE FOREST SCHOOL, _July 1, 1914_.

CONTENTS

PREFACE

PART I THE MECHANICAL PROPERTIES OF WOOD

Introduction
Fundamental considerations and definitions
Tensile strength
Compressive or crushing strength
Shearing strength
Transverse or bending strength: Beams
Toughness: Torsion
Hardness
Cleavability

PART II FACTORS AFFECTING THE MECHANICAL PROPERTIES OF
WOOD

Introduction
Rate of growth
Heartwood and sapwood
Weight, density, and specific gravity
Color
Cross grain
Knots
Frost splits
Shakes, galls, pitch pockets
Insect injuries
Marine wood-borer injuries
Fungous injuries
Parasitic plant injuries
Locality of growth
Season of cutting
Water content
Temperature
Preservatives

PART III TIMBER TESTING

Working plan
Forms of material tested
Size of test specimens
Moisture determination
Machine for static tests
Speed of testing machine
Bending large beams
Bending small beams
Endwise compression
Compression across the grain
Shear along the grain
Impact test
Hardness test: Abrasion and indentation
Cleavage test
Tension test parallel to the grain
Tension test at right angles to the grain
Torsion test
Special tests
Spike pulling test
Packing boxes
Vehicle and implement woods
Cross-arms