bending tests on small clear
beams of 49 woods in green condition
X. Results of impact bending tests on small clear
beams of 34 woods in green condition
XI. Manner of first failure of large beams
XII. Hardness of 32 woods in green condition, as
indicated by the load required to imbed a
0.444-inch steel ball to one-half its diameter
XIII. Cleavage strength of small clear pieces of 32
woods in green condition
XIV. Specific gravity, and shrinkage of 51 American
woods
XV. Effect of drying on the mechanical properties of
wood, shown in ratio of increase due to reducing
moisture content from the green condition to
kiln-dry
XVI. Effect of steaming on the strength of green
loblolly pine
XVII. Speed-strength moduli, and relative increase in
strength at rates of fibre strain increasing in
geometric ratio
XVIII. Results of bending tests on green structural
timbers
XIX. Results of compression and shear tests on green
structural timbers
XX. Results of bending tests on air-seasoned
structural timbers
XXI. Results of compression and shear tests on
air-seasoned structural timbers
XXII. Working unit stresses for structural timber
expressed in pounds per square inch

PART I THE MECHANICAL PROPERTIES OF WOOD

INTRODUCTION

The mechanical properties of wood are its fitness and ability to
resist applied or external forces. By external force is meant
any force outside of a given piece of material which tends to
deform it in any manner. It is largely such properties that
determine the use of wood for structural and building purposes
and innumerable other uses of which furniture, vehicles,
implements, and tool handles are a few common examples.

Knowledge of these properties is obtained through
experimentation either in the employment of the wood in practice
or by means of special testing apparatus in the laboratory.
Owing to the wide range of variation in wood it is necessary
that a great number of tests be made and that so far as possible
all disturbing factors be eliminated. For comparison of
different kinds or sizes a standard metho