structural timbers, both green and air-seasoned, are included.
The relation of the stresses developed in different structural
forms to those developed in the small clear specimens is given.

In the bibliography attempt was made to list all of the
important publications and articles on the mechanical properties
of wood, and timber testing. While admittedly incomplete, it
should prove of assistance to the student who desires a fuller
knowledge of the subject than is presented here.

The writer is indebted to the U.S. Forest Service for nearly all
of his tables and photographs as well as many of the data upon
which the book is based, since only the Government is able to
conduct the extensive investigations essential to a thorough
understanding of the subject. 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_.